CVE-2026-16365VulnerabilityPublished 30 Sep 2026Updated 5 Nov 2026

Red Hat Security Advisory: thunderbird security update

Affects Red Hat thunderbirdSource GCVE Database

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Mentioned vulnerabilities

Authoritative record:CVE-2026-16365· High 8.8

Not known to be exploited · CVSS 8.8 High.

Data as of 5 Nov 2026, 20:49 UTC

CVSS 3.1 base score

8.8High

How severe the flaw is on the 0–10 CVSS scale.

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: Required
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 21 Jul 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Red Hat Product Security Red Hat	Affected <153	Fixed in 153

Description

Mozilla Thunderbird is a standalone mail and newsgroup client. Security Fix(es): * firefox: thunderbird: Privilege escalation in the DOM: Workers component (CVE-2026-16365) * firefox: thunderbird: Sandbox escape in the Remote Settings Client component (CVE-2026-75874) * firefox: Sandbox escape due to use-after-free in the DOM: Security component (CVE-2026-84121) * firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2, Firefox ESR 140.15 and Firefox ESR 115.40 (CVE-2026-84145) * firefox: Sandbox escape due to use-after-free in the DOM: Navigation component (CVE-2026-84119) * firefox: Use-after-free in the Audio/Video component (CVE-2026-84120) * firefox: Privilege escalation due to invalid pointer in the Graphics component (CVE-2026-84131) * firefox: Use-after-free in the DOM: Core & HTML component (CVE-2026-84124) * firefox: Use-after-free in the Audio/Video component (CVE-2026-84122) * firefox: Internally found bugs fixed in Firefox 155, Firefox ESR 153.2 and Firefox ESR 140.15 (CVE-2026-84143) * thunderbird: Uninitialized memory in MIME parsing (CVE-2026-84639) * thunderbird: Information disclosure due to malicious IMAP server response (CVE-2026-84641) * thunderbird: One byte overflow read in mail parser (CVE-2026-84640) * firefox: thunderbird: Use-after-free in the SVG component (CVE-2026-92024) * firefox: thunderbird: Mitigation bypass in the Remote Settings Client component (CVE-2026-92019) * firefox: thunderbird: Use-after-free in the Networking component (CVE-2026-92026) * firefox: thunderbird: Information disclosure in the Graphics: ImageLib component (CVE-2026-92031) * firefox: thunderbird: Sandbox escape due to invalid pointer in the Graphics component (CVE-2026-92032) * firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92010) * firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92006) * firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92011) * firefox: thunderbird: Use-after-free in the DOM: Streams component (CVE-2026-92027) * firefox: thunderbird: Use-after-free in the DOM: Core & HTML component (CVE-2026-92028) * firefox: thunderbird: Privilege escalation in the WebExtensions component (CVE-2026-92015) * firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92013) * firefox: thunderbird: Use-after-free in the Disability Access APIs component (CVE-2026-92016) * firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92012) * firefox: thunderbird: Use-after-free in the DOM: HTML Parser component (CVE-2026-92022) * firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics component (CVE-2026-92014) * firefox: thunderbird: Sandbox escape in the DOM: Core & HTML component (CVE-2026-92018) * firefox: thunderbird: Use-after-free in the JavaScript Engine: JIT component (CVE-2026-92021) * firefox: thunderbird: Use-after-free in the Audio/Video: Web Codecs component (CVE-2026-92005) * firefox: thunderbird: Privilege escalation in the DOM: Service Workers component (CVE-2026-92017) * firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92009) * firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: WebRender component (CVE-2026-92020) * firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92008) * firefox: thunderbird: Mitigation bypass in the DOM: Copy & Paste and Drag & Drop component (CVE-2026-92030) * firefox: thunderbird: Privilege escalation due to incorrect boundary conditions in the Graphics: CanvasWebGL component (CVE-2026-92007) * firefox: thunderbird: Use-after-free in the DOM: Navigation component (CVE-2026-92025) * firefox: thunderbird: Use-after-free in the SVG component (CVE-2026-92029) * firefox: thunderbird: Use-after-free in the XML component (CVE-2026-92023) * thunderbird: Out-of-bounds read in IMAP response parser (CVE-2026-92240) * thunderbird: Thunderbird: Out-of-bounds read via maliciously constructed IMAP line (CVE-2026-92239) * thunderbird: Thunderbird: Memory safety violations via maliciously crafted mail headers (CVE-2026-92238) For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

CWE-266Incorrect Privilege Assignment (opens in a new tab)
Base weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
A product incorrectly assigns a privilege to a particular actor, creating an unintended sphere of control for that actor.
Architecture and Design · Operation
Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
Architecture and Design · Operation · Environment Hardening
Run your code using the lowest privileges that are required to accomplish the necessary tasks. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment.
OWASP Cheat Sheets
Docker Security (opens in a new tab)
Third Party Javascript Management (opens in a new tab)
Virtual Patching (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V1.4.4 (opens in a new tab)
V1.4.5 (opens in a new tab)
V1.10.1 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-653Improper Isolation or Compartmentalization (opens in a new tab)
Class weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product does not properly compartmentalize or isolate functionality, processes, or resources that require different privilege levels, rights, or permissions.
Architecture and Design
Break up privileges between different modules, objects, or entities. Minimize the interfaces between modules and require strong access control between them.
OWASP Cheat Sheets
Secure Design Principles (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-825Expired Pointer Dereference (opens in a new tab)
Base weakness
The product dereferences a pointer that contains a location for memory that was previously valid, but is no longer valid.
Architecture and Design
Choose a language that provides automatic memory management.
Implementation
When freeing pointers, be sure to set them to NULL once they are freed. However, the utilization of multiple or complex data structures may lower the usefulness of this strategy.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-787Out-of-bounds Write (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #5
The product writes data past the end, or before the beginning, of the intended buffer.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Operation · Build and Compilation · Environment Hardening
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index…
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-824Access of Uninitialized Pointer (opens in a new tab)
Base weakness
The product accesses or uses a pointer that has not been initialized.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-125Out-of-bounds Read (opens in a new tab)
Base weaknessCWE Top 25 (2025): #8
The product reads data past the end, or before the beginning, of the intended buffer.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design · Language Selection
Use a language that provides appropriate memory abstractions.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
Attack patterns
Overread Buffers (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-791Incomplete Filtering of Special Elements (opens in a new tab)
Base weakness
The product receives data from an upstream component, but it does not completely filter special elements before sending it to a downstream component.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
Server Side Request Forgery Prevention (opens in a new tab)
Unvalidated Redirects and Forwards (opens in a new tab)
Cross Site Scripting Prevention (opens in a new tab)
OWASP ASVS 4.0.3
V1.5.1 (opens in a new tab)
V5.2.2 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-807Reliance on Untrusted Inputs in a Security Decision (opens in a new tab)
Base weaknessLikelihood of exploit: HighOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product uses a protection mechanism that relies on the existence or values of an input, but the input can be modified by an untrusted actor in a way that bypasses the protection mechanism.
Architecture and Design · Attack Surface Reduction
Store state information and sensitive data on the server side only.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
OWASP Cheat Sheets
Secure Design Principles (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-497Exposure of Sensitive System Information to an Unauthorized Control Sphere (opens in a new tab)
Base weaknessOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not properly prevent sensitive system-level information from being accessed by unauthorized actors who do not have the same level of access to the underlying system as the product does.
Architecture and Design · Implementation
Production applications should never use methods that generate internal details such as stack traces and error messages unless that information is directly committed to a log that is not viewable by the end user.
OWASP Cheat Sheets
Error Handling (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V14.3.2 (opens in a new tab)
V8.3.4 (opens in a new tab)
V14.3.3 (opens in a new tab)
Attack patterns
Web Application Fingerprinting (opens in a new tab)
System Location Discovery (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-476NULL Pointer Dereference (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #13OWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product dereferences a pointer that it expects to be valid but is NULL.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Requirements
Select a programming language that is not susceptible to these issues.
Implementation
Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-843Access of Resource Using Incompatible Type (Type Confusion) (opens in a new tab)
Base weakness
The product allocates or initializes a resource such as a pointer, object, or variable using one type, but it later accesses that resource using a type that is incompatible with the original type.

GCVE source: db.gcve.eu
Csaf Category: csaf_security_advisory
Csaf Version: 2.0
Publisher: Red Hat Product Security
Advisory ID: RHSA-2026:73971
Vendor Severity: high
CVE Count: 44
Additional Cves: CVE-2026-75874, CVE-2026-84119, CVE-2026-84120, CVE-2026-84121, CVE-2026-84122, CVE-2026-84124, CVE-2026-84131, CVE-2026-84143, CVE-2026-84145, CVE-2026-84639, CVE-2026-84640, CVE-2026-84641, CVE-2026-92005, CVE-2026-92006, CVE-2026-92007, CVE-2026-92008, CVE-2026-92009, CVE-2026-92010, CVE-2026-92011, CVE-2026-92012, CVE-2026-92013, CVE-2026-92014, CVE-2026-92015, CVE-2026-92016, CVE-2026-92017, CVE-2026-92018, CVE-2026-92019, CVE-2026-92020, CVE-2026-92021, CVE-2026-92022, CVE-2026-92023, CVE-2026-92024, CVE-2026-92025, CVE-2026-92026, CVE-2026-92027, CVE-2026-92028, CVE-2026-92029, CVE-2026-92030, CVE-2026-92031, CVE-2026-92032, CVE-2026-92238, CVE-2026-92239, CVE-2026-92240

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

WeaknessesCWE-266, CWE-653, CWE-825 +8

Technical details

References

Community reviews

Related threats