CVE-2026-6763: Mitigation bypass in the File Handling component
Analyzed
AliasesUBUNTU-CVE-2026-6763DEBIAN-CVE-2026-6763CGA-8f68-hq4r-pj45CGA-hcrr-j3wr-4xpcCGA-6rpf-x64p-cgjgCGA-q99r-q35g-3vgq
Published 21-04-2026Last modified 26-05-2026
Vulnerability summary
CVE-2026-6763 is a medium (CVSS 6.5) Protection Mechanism Failure vulnerability in mozilla firefox. EPSS estimates a 0.32% chance of exploitation in the next 30 days, higher than 24% of scored vulnerabilities.
CVSS score
6.5/10
010
Medium · v3.1 (CVE.org)EPSS score
0.32%
0%100%
Low · +0.13 pp in 30 daysKEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 32 · Related 4MGASA-2026-0124MGASA-2026-0125OPENSUSE-SU-2026:10610-1OPENSUSE-SU-2026:10626-1OPENSUSE-SU-2026:11373-1RHSA-2026:10757RHSA-2026:10766RHSA-2026:10767RHSA-2026:12285RHSA-2026:13537RHSA-2026:15892RHSA-2026:17477RHSA-2026:17687RHSA-2026:17688RHSA-2026:17689RHSA-2026:17690RHSA-2026:19041RHSA-2026:19131RHSA-2026:19201RHSA-2026:19348RHSA-2026:19461RHSA-2026:19462RHSA-2026:19463RHSA-2026:19464RHSA-2026:19465RHSA-2026:19466RHSA-2026:19467RHSA-2026:19468RHSA-2026:19469RHSA-2026:19542RHSA-2026:19655RHSA-2026:19704CGA-4MJF-4GC7-VM27
Timeline
- 21-04-2026PublishedVulnerability first disclosed.
- 26-05-2026Last modifiedVulnerability information updated.
Description
Mitigation bypass in the File Handling component. This vulnerability was fixed in Firefox 150, Firefox ESR 140.10, Thunderbird 150, and Thunderbird 140.10.
CVSS metrics
4 scores · 4 sources · 1 versionMedium 6.5Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:NSourcesAll 4 agree
- OSV · UbuntuEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- OSV · DebianEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- NVDNIST6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
EPSS trend
Probability
0.32%
Chance of exploitation in the next 30 days
Percentile
24%
Versus all other CVEs
30-day change
Increase +0.13 pp
From 0.19% on 22-09-2026
22-09-202622-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected 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< 140.10-r0
- firefox-esr< 140.10-r0
Debian2 products
- firefox-esr< 140.10.0esr-1~deb12u1 | < 140.10.0esr-1~deb13u1 | < 140.10.0esr-1
- thunderbird< 1:140.10.0esr-1~deb12u1 | < 1:140.10.0esr-1~deb13u1 | < 1:140.10.0esr-1
Mozilla2 products
- firefox< 140.10.0 | < 150.0
- thunderbird≥ 140.0, < 140.10.0
Wolfi1 product
- firefox< 140.10-r0
5 vendors · 15 products
References
10 links- bugzilla.mozilla.org/show_bug.cgi?id=2021666Permissions Required
- www.mozilla.org/security/advisories/mfsa2026-30/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-32/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-33/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-34/Vendor Advisory
