CVE-2026-100765

Use-after-free in the JavaScript: WebAssembly component

Published Sep 29, 2026 CVSS 3.1 · 8.8 High EPSS < 1% KEV · Not listed
Description
Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.

Analysis

AI-generated

Technical impact

The CVE identifies a use-after-free flaw in the JavaScript WebAssembly component of Mozilla products. The description does not explicitly state the consequences. Based on the nature of use-after-free vulnerabilities, the flaw could potentially lead to memory corruption or execution of arbitrary code, but this is inferred. Potential impact may involve compromise of confidentiality, integrity, or availability of the user’s system, though the description does not confirm these outcomes.

Affected Systems

Mozilla Firefox browsers running versions prior to ESR 153.4 and the standard Firefox build 157 are affected, and Thunderbird versions prior to 157 and 153.4 are also affected. Users on earlier ESR or non-ESR releases of Firefox are potentially vulnerable.

Risk and Exploitability

The CVSS score of 8.8 indicates high severity. The EPSS score of less than 1% indicates a low probability of exploitation. The vulnerability is not listed in CISA’s KEV catalog, suggesting no widespread exploitation has been reported. The attack vector is likely remote via malicious WebAssembly modules embedded in web pages; this inference is based on typical exploitation patterns for browser component flaws. Exploitation would require the victim to open a compromised page, as is typical for browser vulnerabilities.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade to Firefox ESR 153.4 or later to receive the WebAssembly engine fix.
  • Upgrade to the latest stable Firefox release, which includes the same fix as of version 157 or newer.
  • Disable WebAssembly in Firefox until a patch is applied, for example by setting javascript.options.wasm to 0 in about:config.

Generated by OpenCVE AI on October 1, 2026 at 02:25 UTC.

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4814-1 firefox-esr security update
Debian DSA Debian DSA DSA-6533-1 firefox-esr security update
History
Type Values Removed Values Added
First Time appeared Mozilla thunderbird
CPEs cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
cpe:2.3:a:mozilla:thunderbird:*:*:*:*:*:*:*:*
Vendors & Products Mozilla thunderbird
Type Values Removed Values Added
Description Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, and Firefox 157. Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 153.4, and Firefox 157.
References
Type Values Removed Values Added
Description Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox ESR 153.4 and Firefox 157. Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, and Firefox 157.
References
Type Values Removed Values Added
First Time appeared Mozilla
Mozilla firefox
Vendors & Products Mozilla
Mozilla firefox
Type Values Removed Values Added
Weaknesses CWE-416
Metrics cvssV3_1

{'score': 8.8, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H'}

ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'total'}, 'version': '2.0.3'}

Type Values Removed Values Added
Description Use-after-free in the JavaScript: WebAssembly component. This vulnerability was fixed in Firefox ESR 153.4 and Firefox 157.
Title Use-after-free in the JavaScript: WebAssembly component
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
mozilla
Published
Updated
Sep 30, 2026, 5:20 PM
Reserved
Sep 26, 2026, 7:15 PM
Status
Analyzed
Published
Sep 29, 2026, 1:17 PM
Modified
Oct 13, 2026, 6:30 PM