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Vulnerabilities

Vulnerability · CVE-2025-5269

Memory safety bug present in Firefox ESR 128.10, and Thunderbird 128.10.

Published May 27, 2025 · catalog updated Apr 13, 2026 · mozilla

Severity
High8.1
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.5%
Remediation
Advisory link
Affected products
vendor mozilla

Memory safety bug present in Firefox ESR 128.10, and Thunderbird 128.10. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.11 and Thunderbird 128.11.

Technical analysis

Mechanism and impact are interpreted from ingested advisories — not independent exploit research.

  • CWE classification

    No CWE identifiers stored yet.

  • Prerequisites and impact

    Follow the original vendor advisory for access prerequisites and impact. This catalog does not invent exploit conditions.

How to fix CVE-2025-5269

What to do

Three reads of the same public record: the decision, the versions on file, and the signals. Confirm the vendor advisory before you patch. This page does not publish exploit steps.

Executive

This is a public record, not a confirmed incident. CVE-2025-5269 is a high issue in mozilla (CVSS 8.1). CISA does not currently list it as known exploited. Next step: Compare installed versions with the linked vendor advisory before changing production.

System administrator

Check whether mozilla is installed. Ranges on record: mozilla. Compare installed versions with the linked vendor advisory before changing production.

Security analyst

CVSS 8.1. EPSS 0.5%. CISA does not currently list it as known exploited. Weaknesses: not classified. Sources: epss, euvd. Exploit links, when listed below, point at the original publisher.

Related intelligence

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. May 27, 2025 · EUVD

    Detected

    Memory safety bug present in Firefox ESR 128.10, and Thunderbird 128.10. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.11 and Thunderbird 128.11.

  2. Apr 13, 2026 · EUVD

    Updated

    Memory safety bug present in Firefox ESR 128.10, and Thunderbird 128.10. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.11 and Thunderbird 128.11.

Affected versions

Enter an installed version to get a verified affected / not-affected result against the ranges below.

  • vendor mozillaversion unspecified

Sources

  • FIRST EPSSExploitation probabilityCVE-2025-5269

    30-day exploitation probability 0.5%

    first.org
  • EUVDVulnerability recordEUVD-2025-18098

    Memory safety bug present in Firefox ESR 128.10, and Thunderbird 128.10. This bug showed evidence of memory corruption and we presume that with enough effort this could have been exploited to run arbitrary code. This vulnerability was fixed in Firefox ESR 128.11 and Thunderbird 1

    euvd.enisa.europa.eu

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.