CVE-2026-8956Network attack vector

Unspecified impact via JAR integer overflow

Published May 19, 2026 · Updated May 19, 2026

Integer overflow in Mozilla's Networking: JAR component affects Firefox and Thunderbird before 151, with unspecified impact. Firefox ESR before 140.11 and Thunderbird ESR before 140.11 are also affected, but Mozilla has not published the overflowing calculation or attacker-controlled input. The restricted security bug leaves the delivery path, required interaction, and bounded consequence undisclosed.

CVSS severity9.8
Critical
EPSS probability0.60%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer overflow in Mozilla's Networking: JAR component affects Firefox and Thunderbird before 151, with unspecified impact. Firefox ESR before 140.11 and Thunderbird ESR before 140.11 are also affected, but Mozilla has not published the overflowing calculation or attacker-controlled input. The restricted security bug leaves the delivery path, required interaction, and bounded consequence undisclosed.

The record

CVE
CVE-2026-8956
Published
May 19, 2026
Updated
May 19, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 19, 2026CVE publishedPublication date reported by the CVE source.
  2. May 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-190Integer Overflow or Wraparound

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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