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VulnerabilityPublished

CVE-2026-8956: Mozilla Firefox · Integer Overflow

Affects Mozilla FirefoxSource CVE Database V5

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Not known to be exploited · CVSS 9.8 Critical · patch available : patch Mozilla Firefox as a priority.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
9.8Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.6% chance of exploitation in 30 days – higher than 48% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 19 May 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
Mozilla FirefoxAffected
  • <151
Fixed in
  • 151

AI-suggested

Mozilla has officially fixed this vulnerability in Firefox 151 and Firefox ESR 140.11. Users should update their Firefox installations to these versions or later to remediate this issue. Since the vulnerability is patched, no additional mitigation steps are required beyond applying the official update.

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.

References

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