CVE-2025-5262Network attack vector

Application crash via failed encoder initialization double-free

Published May 27, 2025 · Updated Aug 25, 2025

Double-free in Thunderbird before 139 and Thunderbird ESR before 128.11 allows remote attackers to corrupt memory via WebRTC encoder initialization. The vpx_codec_enc_init_multi function releases the same allocation twice after allocation failure while initializing the WebRTC encoder. Reachability requires encoder initialization to encounter an allocation failure; successful triggering can crash the application, with no published confidentiality or integrity impact.

CVSS severity7.5
High
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Double-free in Thunderbird before 139 and Thunderbird ESR before 128.11 allows remote attackers to corrupt memory via WebRTC encoder initialization. The vpx_codec_enc_init_multi function releases the same allocation twice after allocation failure while initializing the WebRTC encoder. Reachability requires encoder initialization to encounter an allocation failure; successful triggering can crash the application, with no published confidentiality or integrity impact.

The record

CVE
CVE-2025-5262
Published
May 27, 2025
Updated
Aug 25, 2025
Vendor
Mozilla
Product
Thunderbird
Classifications
CWE-415, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 27, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 25, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <128.11
  2. Affected versionversion=unspecified <139

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Thunderbirdversion=unspecified <128.11; version=unspecified <139

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-415Double Free
T1499Endpoint Denial of Service

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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