CVE-2026-8956: mozilla firefox Integer Overflow or Wraparound
CVSS: 9.8v3.1CriticalAnalyzed
AliasesUBUNTU-CVE-2026-8956DEBIAN-CVE-2026-8956CGA-m378-4qgf-36hpCGA-q4q2-v3jh-p99wCGA-6mh2-5g9r-w98pCGA-mc46-v7mf-gjwm
Published 19-05-2026Last modified 19-05-2026
Vulnerability summary
CVE-2026-8956 is a critical (CVSS 9.8) Integer Overflow or Wraparound vulnerability in mozilla firefox. EPSS estimates a 0.64% chance of exploitation in the next 30 days, higher than 49.7% of scored vulnerabilities.
CVSS score
9.8/10
010
Critical · v3.1 (CVE.org)EPSS score
0.64%
0%100%
Low · +0.04 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 27 · Related 5MGASA-2026-0164MGASA-2026-0165OPENSUSE-SU-2026:10813-1OPENSUSE-SU-2026:10863-1OPENSUSE-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-6CQ3-Q2F5-5CVX
Timeline
- 19-05-2026PublishedVulnerability first disclosed.
- 19-05-2026Last modifiedVulnerability information updated.
Description
Integer overflow in the Networking: JAR component. This vulnerability was fixed in Firefox 151, Firefox ESR 140.11, Thunderbird 151, 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:HSourcesAll 4 agree
- OSV · UbuntuEcosystem advisory · calculated9.8CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- 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
0.64%
Chance of exploitation in the next 30 days
Percentile
50%
Versus all other CVEs
30-day change
+0.04 pp
From 0.60% on 19-09-2026
19-09-202619-10-2026
EPSS score0.64%
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)
Chainguard2 products
- firefox< 140.11-r0
- firefox-esr< 140.11-r0
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
Mozilla2 products
- firefox< 140.11.0 | < 151.0.0
- thunderbird< 140.11 | < 151.0.0
Wolfi1 product
- firefox< 140.11-r0
5 vendors · 15 products
