Red Hat Security Advisory: firefox security update
Affects Red Hat firefoxSource GCVE Database
Mentioned vulnerabilities
Not known to be exploited · CVSS 9.6 Critical.
Data as of 26 Oct 2026, 18:00 UTC
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H- Attack Vector
- Network
- Attack Complexity
- Low
- Privileges Required
- None
- User Interaction
- Required
- Scope
- Changed
- 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: Changed
- An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
- 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 15 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 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.
- Weaponised
- Public exploit code exists in Metasploit or Exploit-DB, 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
| Fixed in
|
AI-suggested
A security update for Firefox is available from Red Hat for Red Hat Enterprise Linux 9 and related variants. Users should apply the update promptly to remediate these vulnerabilities. For detailed update instructions, refer to the Red Hat advisory at https://access.redhat.com/articles/11258. No additional mitigation steps are indicated beyond applying the official update.
Description
Multiple security vulnerabilities affecting Mozilla Firefox and Thunderbird have been addressed in a Red Hat security update. These include sandbox escapes, use-after-free conditions, privilege escalations, information disclosures, and other memory safety issues across various components such as Graphics, DOM, JavaScript WebAssembly, Networking, and Storage. The update is rated as important by Red Hat Product Security and targets Red Hat Enterprise Linux 9 and related variants.
Impact
The vulnerabilities collectively allow attackers to escape sandbox restrictions, escalate privileges, cause use-after-free memory corruption, disclose sensitive information, bypass same-origin policies, and potentially execute arbitrary code or disrupt browser security boundaries. These impacts can compromise the security and integrity of the affected systems running Firefox or Thunderbird on Red Hat Enterprise Linux 9.
- CWE-501Trust Boundary Violation (opens in a new tab)
Base weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product mixes trusted and untrusted data in the same data structure or structured message.
- OWASP Cheat Sheets
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- CWE-201Insertion of Sensitive Information Into Sent Data (opens in a new tab)
Base weaknessOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor.
Requirements
Specify which data in the software should be regarded as sensitive. Consider which types of users should have access to which types of data.
Implementation
Ensure that any possibly sensitive data specified in the requirements is verified with designers to ensure that it is either a calculated risk or mitigated elsewhere.
System Configuration
Setup default error messages so that unexpected errors do not disclose sensitive information.
- OWASP Cheat Sheets
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
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
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- CWE-416Use After Free (opens in a new tab)
Variant weaknessLikelihood of exploit: HighCWE Top 25 (2025): #7
The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer.
Architecture and Design · Language Selection
Choose a language that provides automatic memory management.
Implementation · Attack Surface Reduction
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
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- CWE-284Improper Access Control (opens in a new tab)
Pillar weaknessCWE Top 25 (2025): #19OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Operation
Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
- OWASP Cheat Sheets
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- CWE-457Use of Uninitialized Variable (opens in a new tab)
Variant weaknessLikelihood of exploit: High
The code uses a variable that has not been initialized, leading to unpredictable or unintended results.
Implementation · Attack Surface Reduction
Ensure that critical variables are initialized before first use.
Build and Compilation · Compilation or Build Hardening
Most compilers will complain about the use of uninitialized variables if warnings are turned on.
Implementation · Operation
When using a language that does not require explicit declaration of variables, run or compile the software in a mode that reports undeclared or unknown variables. This may indicate the presence of a typographic error in the variable's name.
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
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- CWE-200Exposure of Sensitive Information to an Unauthorized Actor (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #20OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
- OWASP Cheat Sheets
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- CWE-758Reliance on Undefined, Unspecified, or Implementation-Defined Behavior (opens in a new tab)
Class weakness
The product uses an API function, data structure, or other entity in a way that relies on properties that are not always guaranteed to hold for that entity.
- CWE-693Protection Mechanism Failure (opens in a new tab)
Pillar weaknessOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
- OWASP Cheat Sheets
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- CWE-908Use of Uninitialized Resource (opens in a new tab)
Base weaknessLikelihood of exploit: Medium
The product uses or accesses a resource that has not been initialized.
Implementation
Explicitly initialize the resource before use. If this is performed through an API function or standard procedure, follow all required steps.
Implementation
Pay close attention to complex conditionals that affect initialization, since some branches might not perform the initialization.
Implementation
Avoid race conditions (CWE-362) during initialization routines.
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
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.
- CWE-269Improper Privilege Management (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product does not properly assign, modify, track, or check privileges for an actor, creating an unintended sphere of control for that actor.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Operation
Very carefully manage the setting, management, and handling of privileges. Explicitly manage trust zones in the software.
Architecture and Design · Separation of Privilege
Follow the principle of least privilege when assigning access rights to entities in a software system.
Architecture and Design · Separation of Privilege
Consider following the principle of separation of privilege. Require multiple conditions to be met before permitting access to a system resource.
- OWASP Cheat Sheets
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- CWE-346Origin Validation Error (opens in a new tab)
Class weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not properly verify that the source of data or communication is valid.
- OWASP Cheat Sheets
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- CWE-15External Control of System or Configuration Setting (opens in a new tab)
Base weaknessOWASP Top 10 A02:2025: Security Misconfiguration (opens in a new tab)
One or more system settings or configuration elements can be externally controlled by a user.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
Implementation · Architecture and Design
Because setting manipulation covers a diverse set of functions, any attempt at illustrating it will inevitably be incomplete. Rather than searching for a tight-knit relationship between the functions addressed in the setting manipulation category, take a step back and consider the sorts of system values that an…
Implementation · Architecture and Design
In general, do not allow user-provided or otherwise untrusted data to control sensitive values. The leverage that an attacker gains by controlling these values is not always immediately obvious, but do not underestimate the creativity of the attacker.
- OWASP Cheat Sheets
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
- GCVE source
- db.gcve.eu
- Csaf Category
- csaf_security_advisory
- Csaf Version
- 2.0
- Publisher
- Red Hat Product Security
- Advisory ID
- RHSA-2026:76761
- Vendor Severity
- high
- CVE Count
- 43
- Additional Cves
- CVE-2026-96869, CVE-2026-100756, CVE-2026-100757, CVE-2026-100758, CVE-2026-100759, CVE-2026-100762, CVE-2026-100766, CVE-2026-100767, CVE-2026-100769, CVE-2026-100770, CVE-2026-100771, CVE-2026-100772, CVE-2026-100773, CVE-2026-100774, CVE-2026-100775, CVE-2026-100776, CVE-2026-100777, CVE-2026-100778, CVE-2026-100779, CVE-2026-100780, CVE-2026-100781, CVE-2026-100782, CVE-2026-100783, CVE-2026-100784, CVE-2026-100785, CVE-2026-100786, CVE-2026-100788, CVE-2026-100789, CVE-2026-100790, CVE-2026-100791, CVE-2026-100792, CVE-2026-100794, CVE-2026-100797, CVE-2026-100801, CVE-2026-100803, CVE-2026-100807, CVE-2026-100811, CVE-2026-100818, CVE-2026-100819, CVE-2026-100820, CVE-2026-100821, CVE-2026-100832
References
- access.redhat.com/errata/RHSA-2026:76761 (opens in a new tab)
- access.redhat.com/security/updates/classification/ (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2533789 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543113 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543114 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543116 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543120 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543121 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543123 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543125 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543128 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543130 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543131 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543133 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543134 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543137 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543140 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543142 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543144 (opens in a new tab)
- bugzilla.redhat.com/show_bug.cgi?id=2543145 (opens in a new tab)
Community reviews
Related threats
- CVE-2026-100832: Mozilla Firefox · Use After FreeHighVulnerability
- CVE-2026-100784: Mozilla Firefox · Use After FreeHighVulnerability
- CVE-2026-100832: thunderbird security updateUnratedVulnerability
- Red Hat Security Advisory: thunderbird security updateHighVulnerability
- Red Hat Security Advisory: thunderbird security updateHighVulnerability