VulnerabilityPublished 27 Oct 2026Updated 5 Nov 2026

CVE-2026-117865: Use-after-free in the JavaScript · GC component

Affects mozjs52Source GCVE Database

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Authoritative record:CVE-2026-117865· Medium 6.3

Not known to be exploited · CVSS 6.3 Medium.

Data as of 6 Nov 2026, 05:33 UTC

CVSS 3.1 base score

6.3Medium

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	6.3

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

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

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: 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: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 27 Oct 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
Ubuntu 24.04 LTSmozjs102`pkg:deb/ubuntu/mozjs102?arch=source&distro=noble`Other threats	Affected =102.15.1-1 =102.15.1-3ubuntu2	Fixed in–
Ubuntu 24.04 LTSmozjs115`pkg:deb/ubuntu/mozjs115?arch=source&distro=noble`Other threats	Affected 115.3.0-0ubuntu1 – 115.10.0-1 9 affected builds	Fixed in–
Ubuntu 22.04 LTSmozjs102`pkg:deb/ubuntu/mozjs102?arch=source&distro=jammy`Other threats	Affected 102.11.0-0ubuntu0.22.04.1 – 102.15.1-0ubuntu0.22.04.1 4 affected builds	Fixed in–
Ubuntu 22.04 LTSmozjs78`pkg:deb/ubuntu/mozjs78?arch=source&distro=jammy`Other threats	Affected =78.13.0-1 =78.15.0-2 =78.15.0-4ubuntu1	Fixed in–
Ubuntu 22.04 LTSmozjs91`pkg:deb/ubuntu/mozjs91?arch=source&distro=jammy`Other threats	Affected 91.5.1-0ubuntu1 – 91.10.0-0ubuntu1 5 affected builds	Fixed in–
Ubuntu 22.04 LTSthunderbird`pkg:deb/ubuntu/thunderbird?arch=source&distro=jammy`Other threats	Affected 1:91.1.2+build1-0ubuntu1 – 1:140.7.1+build1-0ubuntu0.22.04.1 39 affected builds	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Users and administrators should update affected Mozilla products to Firefox 159, Firefox ESR 153.6, Thunderbird 159, Thunderbird 153.6, or later versions where the vulnerability is fixed. Applying these official updates fully mitigates the vulnerability. No additional action is required beyond applying the vendor-provided patches.

Description

CVE-2026-117865 is a use-after-free vulnerability in the JavaScript garbage collection (GC) component of Mozilla products. This flaw was addressed and fixed in Firefox 159, Firefox ESR 153.6, Thunderbird 159, and Thunderbird 153.6. The vulnerability has a medium severity rating with a CVSS score of 6.3, indicating potential impacts on confidentiality, integrity, and availability. No known exploits are reported in the wild at this time.

Impact

Successful exploitation of this use-after-free vulnerability could allow an attacker to cause a denial of service or potentially execute arbitrary code, impacting confidentiality, integrity, and availability of the affected software. However, no active exploitation in the wild has been reported. The medium severity rating reflects these potential impacts.

Summary

This vulnerability involves a use-after-free condition in the JavaScript GC component within Mozilla products. Use-after-free bugs occur when a program continues to use memory after it has been freed, potentially leading to memory corruption or arbitrary code execution. The issue was fixed in Firefox 159 and corresponding ESR and Thunderbird versions. The CVSS 3.1 vector indicates network attack vector, low attack complexity, no privileges required, user interaction required, unchanged scope, and impacts on confidentiality, integrity, and availability at a low level. The vendor advisory confirms the fix and provides references to the underlying bug report.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Nov 2026, 05:33 UTC

Technical details

References

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