VulnerabilityPublished 29 Sep 2026Updated 10 Nov 2026

CVE-2026-84782: OpenSSL · Out-of-bounds Read

Affects OpenSSLSource CVE Database V5

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Not known to be exploited · CVSS 8.2 High · fixed in 4.0.3 : patch OpenSSL soon.

Data as of 10 Nov 2026, 13:17 UTC

CVSS 3.1 base score

8.2High

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

Thin evidence

One scorer or none

CVSS scores by source
CISA-ADP	CVSS 3.1	8.2

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers can reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-09-29.

Patch

Available – fixed in 4.0.3, 3.6.5, 3.5.9 +4

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
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: None: The vulnerable system can be exploited without any interaction from any user.
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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within 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 29 Sep 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 10 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

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
OpenSSLOpenSSL	Affected >=4.0.0 <4.0.3	Fixed in 4.0.3
OpenSSLOpenSSL	Affected >=3.6.0 <3.6.5	Fixed in 3.6.5
OpenSSLOpenSSL	Affected >=3.5.0 <3.5.9	Fixed in 3.5.9
OpenSSLOpenSSL	Affected >=3.4.0 <3.4.8	Fixed in 3.4.8
OpenSSLOpenSSL	Affected >=3.0.0 <3.0.23	Fixed in 3.0.23
OpenSSLOpenSSL	Affected >=1.1.1 <1.1.1zj	Fixed in 1.1.1zj

AI-suggested

Fixed versions are available: 4.0.3, 3.6.5, 3.5.9, 3.4.8, 3.0.23, 1.1.1zj, and 1.0.2zs. Users should upgrade to these versions to remediate the vulnerability. No other mitigation or workaround is indicated. The vulnerability is not present in the FIPS module.

Description

CVE-2026-84782 is an out-of-bounds read vulnerability in OpenSSL's DTLS retransmission logic. It occurs when a handshake message write is suspended mid-message and a retransmission is triggered, causing the retransmitted message to read beyond its buffer. This can disclose heap memory as plaintext handshake data or cause a crash leading to denial of service. The issue affects multiple OpenSSL versions prior to fixed releases. The vulnerability has a high severity with a CVSS score of 8.2.

Impact

An attacker can receive unintended heap memory contents as plaintext handshake data, potentially leaking sensitive information. Alternatively, the out-of-bounds read can cause the application to crash, resulting in denial of service. There is no indication of privilege escalation or remote code execution. The vulnerability affects confidentiality and availability.

Summary

The DTLS retransmission logic in OpenSSL does not correctly handle cases where a handshake message write is suspended part-way through. When retransmission occurs during such a suspended write, the retransmission logic reuses the same internal buffer and position tracking without resetting the read position to the start of the retransmitted message. This causes the retransmitted message to include leftover bytes from the suspended message, potentially reading past the allocated buffer. This out-of-bounds read can disclose heap memory to the peer or cause a crash and denial of service. Additionally, retransmissions overwrite internal state needed to resume suspended writes, causing aborts in debugging builds. The fix involves resetting the retransmission read position and skipping retransmission if a handshake write is suspended.

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).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 10 Nov 2026, 13:17 UTC

WeaknessesCWE-125

Technical details

References

Community reviews

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