CVE-2026-12296: mozilla firefox Protection Mechanism Failure
CVSS: 9.6v3.1CriticalModified
AliasesUBUNTU-CVE-2026-12296DEBIAN-CVE-2026-12296CGA-469m-vc83-xr92CGA-554r-pw5j-6w8hCGA-2485-4g57-ccjmCGA-52wf-6c6r-wcf2
Published 16-06-2026Last modified 15-07-2026
Vulnerability summary
CVE-2026-12296 is a critical (CVSS 9.6) Protection Mechanism Failure vulnerability in mozilla firefox. EPSS estimates a 0.39% chance of exploitation in the next 30 days, higher than 31.9% of scored vulnerabilities.
CVSS score
9.6/10
010
Critical · v3.1 (CVE.org)EPSS score
0.39%
0%100%
Low · 0.00 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 37 · Related 14MGASA-2026-0242MGASA-2026-0243MGASA-2026-0326OPENSUSE-SU-2026:11052-1OPENSUSE-SU-2026:11055-1OPENSUSE-SU-2026:11072-1OPENSUSE-SU-2026:21043-1OPENSUSE-SU-2026:21168-1OPENSUSE-SU-2026:21519-1RHSA-2026:27717RHSA-2026:27733RHSA-2026:27734RHSA-2026:29940RHSA-2026:30846RHSA-2026:33445RHSA-2026:36100RHSA-2026:36101RHSA-2026:36102RHSA-2026:36103RHSA-2026:37210RHSA-2026:37391RHSA-2026:38506RHSA-2026:38750RHSA-2026:38751RHSA-2026:38753RHSA-2026:39011RHSA-2026:39141RHSA-2026:39142RHSA-2026:39428RHSA-2026:39706SUSE-SU-2026:22351-1SUSE-SU-2026:23115-1SUSE-SU-2026:23137-1SUSE-SU-2026:2582-1SUSE-SU-2026:2583-1SUSE-SU-2026:2814-1SUSE-SU-2026:2852-1CGA-4H66-C47G-54GF
Timeline
- 16-06-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
Description
Sandbox escape in the Security: Process Sandboxing component. This vulnerability was fixed in Firefox 152, Firefox ESR 140.12, Thunderbird 152, and Thunderbird 140.12.
CVSS metrics
4 scores · 4 sources · 1 versionCritical 9.6Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:HSources4 sources · 7.5–9.6
- OSV · UbuntuEcosystem advisory · calculated7.5HighCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:HDiffers
- OSV · DebianEcosystem advisory · calculated9.6CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
- NVDNIST9.6CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
EPSS trend
Probability
0.39%
Chance of exploitation in the next 30 days
Percentile
32%
Versus all other CVEs
30-day change
0.00 pp
From 0.39% on 19-09-2026
19-09-202619-10-2026
EPSS score0.39%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root cause- CWE-693Protection Mechanism FailureThe product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product.
- CWE-403Exposure of File Descriptor to Unintended Control Sphere ('File Descriptor Leak')A process does not close sensitive file descriptors before invoking a child process, which allows the child to perform unauthorized I/O operations using those descriptors.
Affected systems
Ubuntu8 products
- mozjs102All versions (No fix recorded)
- mozjs115All versions (No fix recorded)
- mozjs38All versions (No fix recorded)
- mozjs52All versions (No fix recorded)
- mozjs68All versions (No fix recorded)
Chainguard2 products
- firefox< 140.12-r0
- firefox-esr< 140.12-r0
Debian2 products
- firefox-esr< 140.12.0esr-1~deb12u1 | < 140.12.0esr-1~deb13u1 | < 140.12.0esr-1
- thunderbird< 1:140.12.0esr-1~deb12u1 | < 1:140.12.0esr-1~deb13u1 | < 1:140.12.0esr-1
Mozilla2 products
- firefox< 140.12.0 | < 152.0.0
- thunderbird< 140.12.0 | < 152.0.0
Wolfi1 product
- firefox< 140.12-r0
5 vendors · 15 products
References
35 links- bugzilla.mozilla.org/show_bug.cgi?id=2040515Permissions Required
- www.mozilla.org/security/advisories/mfsa2026-57/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-58/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-60/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-61/Vendor Advisory
