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Vulnerability · Published Jun 16, 2026 · Assigned by mozilla

CVE-2026-12291Use-after-free in the Networking: HTTP component

High 8.8

In plain English

A high-severity use-after-free in Firefox from Mozilla. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 32% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.8High
Exploit odds (30 days)0.4%top 67.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
AlmaLinux:10firefox140.12.0-1.el10_2ALSA-2026:27733
AlmaLinux:8firefox140.12.0-1.el8_10.alma.1ALSA-2026:27717
AlmaLinux:9firefox140.12.0-1.el9_8.alma.1ALSA-2026:27734
AlmaLinux:9firefox-x11140.12.0-1.el9_8.alma.1ALSA-2026:27734
AlmaLinux:10thunderbird140.12.0-1.el10_2.alma.1ALSA-2026:30846
AlmaLinux:8thunderbird140.12.0-1.el8_10.alma.1ALSA-2026:33445
AlmaLinux:9thunderbird140.12.0-1.el9_8.alma.1ALSA-2026:29940
Debian:12firefox-esr140.12.0esr-1~deb12u1DEBIAN-CVE-2026-12291
Debian:13firefox-esr140.12.0esr-1~deb13u1DEBIAN-CVE-2026-12291
Debian:14firefox-esr140.12.0esr-1DEBIAN-CVE-2026-12291
Debian:12thunderbird1:140.12.0esr-1~deb12u1DEBIAN-CVE-2026-12291
Debian:13thunderbird1:140.12.0esr-1~deb13u1DEBIAN-CVE-2026-12291
Debian:14thunderbird1:140.12.0esr-1DEBIAN-CVE-2026-12291
Rocky Linux:10firefox0:140.12.0-1.el10_2RLSA-2026:27733
Rocky Linux:8firefox0:140.12.0-1.el8_10RLSA-2026:27717
Rocky Linux:9firefox0:140.12.0-1.el9_8RLSA-2026:27734
Rocky Linux:10thunderbird0:140.12.0-1.el10_2RLSA-2026:30846
Rocky Linux:8thunderbird0:140.12.0-1.el8_10RLSA-2026:33445
Rocky Linux:9thunderbird0:140.12.0-1.el9_8RLSA-2026:29940
Ubuntu:22.04:LTSmozjs102no fix listedUBUNTU-CVE-2026-12291
Ubuntu:24.04:LTSmozjs102no fix listedUBUNTU-CVE-2026-12291
Ubuntu:24.04:LTSmozjs115no fix listedUBUNTU-CVE-2026-12291
Ubuntu:22.04:LTSmozjs78no fix listedUBUNTU-CVE-2026-12291
Ubuntu:22.04:LTSmozjs91no fix listedUBUNTU-CVE-2026-12291
Ubuntu:22.04:LTSthunderbirdno fix listedUBUNTU-CVE-2026-12291

Affected products (as reported)

VendorProductVersions
Mozilla Firefox see references
Mozilla Thunderbird see references

Weakness: CWE-416, CWE-825 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

References