CVE-2026-8401: mozilla firefox Protection Mechanism Failure
CVSS: 9.8v3.1CriticalModified
AliasesUBUNTU-CVE-2026-8401DEBIAN-CVE-2026-8401CGA-rxpx-3fqj-q5v7CGA-vhw5-2j4r-hgv8
Published 12-05-2026Last modified 15-07-2026
Vulnerability summary
CVE-2026-8401 is a critical (CVSS 9.8) Protection Mechanism Failure vulnerability in mozilla firefox. EPSS estimates a 0.60% chance of exploitation in the next 30 days, higher than 47.4% of scored vulnerabilities.
CVSS score
9.8/10
010
Critical · v3.1 (CVE.org)EPSS score
0.60%
0%100%
Low · +0.28 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 26 · Related 4MGASA-2026-0164MGASA-2026-0165OPENSUSE-SU-2026:10813-1OPENSUSE-SU-2026:10864-1OPENSUSE-SU-2026:21168-1RHSA-2026:21378RHSA-2026:21380RHSA-2026:21381RHSA-2026:21382RHSA-2026:22325RHSA-2026:22643RHSA-2026:26174RHSA-2026:26268RHSA-2026:26269RHSA-2026:26270RHSA-2026:26491RHSA-2026:26492RHSA-2026:26493RHSA-2026:26521RHSA-2026:26536RHSA-2026:26539RHSA-2026:26551RHSA-2026:26606RHSA-2026:26629RHSA-2026:26630RHSA-2026:27715CGA-CR2C-CMFC-VWF2
Timeline
- 12-05-2026PublishedVulnerability first disclosed.
- 15-07-2026Last modifiedVulnerability information updated.
Description
Sandbox escape in the Profile Backup component. This vulnerability was fixed in Firefox 150.0.3, Firefox ESR 115.36, Firefox ESR 140.11, and Thunderbird 140.11.
CVSS metrics
4 scores · 4 sources · 1 versionCritical 9.8Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HSources4 sources · 7.5–9.8
- 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 · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- NVDNIST9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.60%
Chance of exploitation in the next 30 days
Percentile
47%
Versus all other CVEs
30-day change
+0.28 pp
From 0.31% on 19-09-2026
19-09-202619-10-2026
EPSS score0.60%
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-653Improper Isolation or CompartmentalizationThe product does not properly compartmentalize or isolate functionality, processes, or resources that require different privilege levels, rights, or permissions.
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)
Debian2 products
- firefox-esr< 140.11.0esr-1~deb12u1 | < 140.11.0esr-1~deb13u1 | < 140.11.0esr-1
- thunderbird< 1:140.11.0esr-1~deb12u1 | < 1:140.11.0esr-1~deb13u1 | < 1:140.11.0esr-1
Chainguard1 product
- firefox< 150.0.3-r0
Mozilla1 product
- firefox< 150.0.3
Wolfi1 product
- firefox< 150.0.3-r0
5 vendors · 13 products
References
33 links- bugzilla.mozilla.org/show_bug.cgi?id=2038679Permissions Required
- www.mozilla.org/security/advisories/mfsa2026-45/Vendor Advisory
