CVE-2025-1009Public exploitNetwork attack vector

Application crash via stale XSLT document pointer

Published Feb 4, 2025 · Updated Apr 13, 2026

Use-after-free in Mozilla Firefox and Thunderbird allows remote attackers to crash the application through crafted XSLT data. After stylesheet compilation fails, txMozillaXSLTProcessor::NodeWillBeDestroyed returns early and leaves mStylesheetDocument pointing to a freed document that Reset accesses while removing a mutation observer. Hostile XSLT must drive this document-lifetime sequence; affected releases are Firefox before 135, Firefox ESR before 115.20 and 128.1.0 through 128.6, Thunderbird ESR 128.0.1 through 128.6, and Thunderbird 131 through 134.

CVSS severity9.8
Critical
EPSS probability1.21%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Use-after-free in Mozilla Firefox and Thunderbird allows remote attackers to crash the application through crafted XSLT data. After stylesheet compilation fails, txMozillaXSLTProcessor::NodeWillBeDestroyed returns early and leaves mStylesheetDocument pointing to a freed document that Reset accesses while removing a mutation observer. Hostile XSLT must drive this document-lifetime sequence; affected releases are Firefox before 135, Firefox ESR before 115.20 and 128.1.0 through 128.6, Thunderbird ESR 128.0.1 through 128.6, and Thunderbird 131 through 134.

The record

CVE
CVE-2025-1009
Published
Feb 4, 2025
Updated
Apr 13, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-416
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 4, 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

9.8NIST NVDCVSS: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 exploitPublished

Weakness, pattern, technique

CWE-416Use After Free

Public exploit references

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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