CVE-2025-0241Public exploitNetwork attack vector

Application crash via segment-buffer encoding mismatch

Published Jan 7, 2025 · Updated Apr 13, 2026

Memory corruption in Firefox and Thunderbird before 134 allows remote attackers to crash the application via crafted text segmentation. CreateBreakIterator selects an ICU4X iterator from the JavaScript string encoding instead of the stored segment-buffer encoding, causing a char16_t buffer to be interpreted as unsigned bytes. Firefox ESR and Thunderbird ESR before 128.6 share the flaw; Thunderbird mail reading disables scripting, limiting exposure to browser-like contexts.

CVSS severity7.7
High
EPSS probability0.74%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory corruption in Firefox and Thunderbird before 134 allows remote attackers to crash the application via crafted text segmentation. CreateBreakIterator selects an ICU4X iterator from the JavaScript string encoding instead of the stored segment-buffer encoding, causing a char16_t buffer to be interpreted as unsigned bytes. Firefox ESR and Thunderbird ESR before 128.6 share the flaw; Thunderbird mail reading disables scripting, limiting exposure to browser-like contexts.

The record

CVE
CVE-2025-0241
Published
Jan 7, 2025
Updated
Apr 13, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-401
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 7, 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

7.7CISA ADP VulnrichmentCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L

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-401Missing Release of Memory after Effective Lifetime

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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