CVE-2026-100771: mozilla firefox
CVSS: 8.1v3.1HighAnalyzed
AliasesUBUNTU-CVE-2026-100771DEBIAN-CVE-2026-100771
Published 29-09-2026Last modified 01-10-2026
Vulnerability summary
CVE-2026-100771 is a high (CVSS 8.1) vulnerability in mozilla firefox. EPSS estimates a 0.31% chance of exploitation in the next 30 days, higher than 22.2% of scored vulnerabilities.
CVSS score
8.1/10
010
High · v3.1 (CVE.org)EPSS score
0.31%
0%100%
Low · Change unavailableKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 10 · Related 8Timeline
- 29-09-2026PublishedVulnerability first disclosed.
- 01-10-2026Last modifiedVulnerability information updated.
Description
Undefined behavior in the DOM: Streams component. This vulnerability was fixed in Firefox ESR 153.4, Thunderbird 157, Thunderbird 140.17, Thunderbird 153.4, Firefox 157, Firefox ESR 115.42, and Firefox ESR 140.17.
CVSS metrics
4 scores · 4 sources · 1 versionHigh 8.1Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:NSourcesAll 4 agree
- OSV · UbuntuEcosystem advisory · calculated8.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
- OSV · DebianEcosystem advisory · calculated8.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
- NVDNIST8.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
EPSS trend
Probability
0.31%
Chance of exploitation in the next 30 days
Percentile
22%
Versus all other CVEs
30-day change
Change unavailable
Change unavailable
30-09-202619-10-2026
EPSS score0.31%
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< 153.4.0esr-1~deb12u1 | < 153.4.0esr-1~deb13u1 | < 153.4.0esr-1
- thunderbird< 1:140.17.0esr-1~deb12u1 | < 1:140.17.0esr-1~deb13u1 | < 1:153.4.0esr-1
Mozilla2 products
- firefox≥ 115.0, < 115.42.0 | ≥ 140.0.0, < 140.17.0 | ≥ 153.0, < 153.4.0 | ≥ 154.0.0, < 157.0.0
- thunderbird≥ 140.0, < 140.17.0 | ≥ 153.0, < 153.4.0 | ≥ 154.0, < 157.0
3 vendors · 12 products
References
13 links- www.mozilla.org/security/advisories/mfsa2026-101/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-102/Vendor Advisory
- www.mozilla.org/security/advisories/mfsa2026-103/Vendor Advisory
