CVE-2025-1933Public exploitNetwork attack vector

JIT value corruption via unwidened WASM returns

Published Mar 4, 2025 · Updated Jun 4, 2026

JIT memory corruption in Mozilla Firefox and Thunderbird allows remote attackers to alter typed values via crafted WebAssembly. On 64-bit CPUs, GenerateJitEntry boxes an i32 return without first widening it, so stale upper register bits can corrupt the JS::Value tag. User interaction with attacker-controlled content is required; affected lines include Firefox and Thunderbird before 136, Firefox ESR before 115.21 and 128.8, and Thunderbird ESR before 128.8, and invalid values can crash the process or corrupt type tags.

CVSS severity7.6
High
EPSS probability0.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

JIT memory corruption in Mozilla Firefox and Thunderbird allows remote attackers to alter typed values via crafted WebAssembly. On 64-bit CPUs, GenerateJitEntry boxes an i32 return without first widening it, so stale upper register bits can corrupt the JS::Value tag. User interaction with attacker-controlled content is required; affected lines include Firefox and Thunderbird before 136, Firefox ESR before 115.21 and 128.8, and Thunderbird ESR before 128.8, and invalid values can crash the process or corrupt type tags.

The record

CVE
CVE-2025-1933
Published
Mar 4, 2025
Updated
Jun 4, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 4, 2025CVE publishedPublication date reported by the CVE source.
  2. Jun 4, 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

7.6CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/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 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 exploitPublished

Weakness, pattern, technique

T1203Exploitation for Client Execution

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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