Cyber Resilience

CVE-2026-12291

HighUpdated

Published: 16 June 2026

Published
16 June 2026
Modified
30 June 2026
KEV Added
—
Patch
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CVSS Score v3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS Score 0.0038 30.1th percentile
Risk Priority 55 floored blend · peak EPSS

Summary

CVE-2026-12291 is a high-severity Use After Free (CWE-416) vulnerability in Mozilla Firefox. Its CVSS base score is 8.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Drive-by Compromise (T1189); ranked at the 30.1th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

Use-after-free in the Networking: HTTP component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Firefox ESR 115.37, Thunderbird 152, and Thunderbird 140.12.

CWE(s)
CWE-416CWE-825

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1189 Drive-by Compromise Initial Access
Adversaries may gain access to a system through a user visiting a website over the normal course of browsing.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
Why these techniques?

Use-after-free in browser HTTP networking directly enables drive-by client exploitation leading to code execution.

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

Affected Assets

mozilla
firefox
≤ 115.37.0 · ≤ 152.0.0 · 128.0 — 140.12.0
mozilla
thunderbird
≤ 140.12.0 · ≤ 152.0.0

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SI-16 Memory Protection
addresses: CWE-416

Use-after-free exploits that achieve arbitrary code execution are blocked or significantly hardened by non-executable pages and ASLR.

References