CVE-2025-4091Network attack vector

Arbitrary code execution through memory corruption

Published Apr 29, 2025 · Updated Apr 13, 2026

Memory-safety flaws in Mozilla Firefox 137 and ESR 128.9 and Thunderbird 137 and 128.9 let attackers corrupt memory via unspecified vectors. Mozilla identifies two underlying bug reports but has not publicly disclosed the affected code paths or the invalid memory operations. CISA assesses remote, unauthenticated reachability without user interaction; successful exploitation can execute arbitrary code but requires high attack complexity.

CVSS severity8.1
High
EPSS probability0.48%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory-safety flaws in Mozilla Firefox 137 and ESR 128.9 and Thunderbird 137 and 128.9 let attackers corrupt memory via unspecified vectors. Mozilla identifies two underlying bug reports but has not publicly disclosed the affected code paths or the invalid memory operations. CISA assesses remote, unauthenticated reachability without user interaction; successful exploitation can execute arbitrary code but requires high attack complexity.

The record

CVE
CVE-2025-4091
Published
Apr 29, 2025
Updated
Apr 13, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-119, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 29, 2025CVE publishedPublication date reported by the CVE source.
  2. Apr 13, 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

8.1CISA-ADPCVSS:3.1/AV:N/AC:H/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-119Improper Restriction of Operations within the Bounds of a Memory Buffer
T1203Exploitation for Client Execution

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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