CVE-2026-74939: mozilla firefox Improper Privilege Management
CVSS: 8.8v3.1HighAnalyzed
AliasesUBUNTU-CVE-2026-74939DEBIAN-CVE-2026-74939
Published 18-08-2026Last modified 21-08-2026
Vulnerability summary
CVE-2026-74939 is a high (CVSS 8.8) Improper Privilege Management vulnerability in mozilla firefox. EPSS estimates a 0.45% chance of exploitation in the next 30 days, higher than 38.1% of scored vulnerabilities.
CVSS score
8.8/10
010
High · v3.1 (CVE.org)EPSS score
0.45%
0%100%
Low · +0.15 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-2026-0345MGASA-2026-0346OPENSUSE-SU-2026:11546-1OPENSUSE-SU-2026:11558-1OPENSUSE-SU-2026:11580-1OPENSUSE-SU-2026:21594-1OPENSUSE-SU-2026:21713-1RHSA-2026:58897RHSA-2026:58898RHSA-2026:58899RHSA-2026:64813RHSA-2026:64814RHSA-2026:65103RHSA-2026:65105RHSA-2026:65110RHSA-2026:65111RHSA-2026:65158RHSA-2026:65159RHSA-2026:65160RHSA-2026:65442RHSA-2026:65633RHSA-2026:65669RHSA-2026:65670RHSA-2026:65757RHSA-2026:65764RHSA-2026:65765RHSA-2026:65766RHSA-2026:65888SUSE-SU-2026:23304-1SUSE-SU-2026:23411-1SUSE-SU-2026:23590-1SUSE-SU-2026:3658-1SUSE-SU-2026:3683-1SUSE-SU-2026:3897-1SUSE-SU-2026:4140-1SUSE-SU-2026:4156-1SUSE-SU-2026:4268-1
Timeline
- 18-08-2026PublishedVulnerability first disclosed.
- 21-08-2026Last modifiedVulnerability information updated.
Description
Privilege escalation in the DOM: Navigation component. This vulnerability was fixed in Firefox 154, Firefox ESR 115.39, Firefox ESR 140.14, Firefox ESR 153.1, Thunderbird 154, Thunderbird 140.14, and Thunderbird 153.1.
CVSS metrics
4 scores · 4 sources · 1 versionHigh 8.8Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HSourcesAll 4 agree
- OSV · UbuntuEcosystem advisory · calculated8.8HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated8.8HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- NVDNIST8.8HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.45%
Chance of exploitation in the next 30 days
Percentile
38%
Versus all other CVEs
30-day change
+0.15 pp
From 0.30% on 20-09-2026
20-09-202620-10-2026
EPSS score0.45%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
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)
Debian2 products
- firefox-esr< 140.14.0esr-1~deb12u1 | < 140.14.0esr-1~deb13u1 | < 140.14.0esr-2
- thunderbird< 1:140.14.0esr-1~deb12u1 | < 1:140.14.0esr-1~deb13u1 | < 1:140.14.0esr-1
Mozilla2 products
- firefox< 115.39.0 | ≥ 116.0, < 140.14.0 | ≥ 141.0, < 153.1.0
- thunderbird< 140.14.0 | ≥ 141.0, < 153.1.0
3 vendors · 12 products
References
14 links- bugzilla.mozilla.org/show_bug.cgi?id=2054416Permissions Required
- www.mozilla.org/security/advisories/mfsa2026-74/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-75/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-76/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-77/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-78/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-79/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-80/Vendor Advisory
