CVE-2022-31740Public exploitNetwork attack vector

Crash via incorrect WASM register allocation

Published Dec 22, 2022 · Updated Apr 16, 2025

Incorrect WASM assembly generation in affected Mozilla Firefox and Thunderbird releases allows remote attackers to crash arm64 clients. The arm64 JIT lowering for f32.copysign treats the second operand as start-only while reusing the first operand's register, allowing output to clobber a live input and violate allocation integrity. A victim must process attacker-controlled WASM on an arm64 build; Firefox before 101, Firefox ESR before 91.10, and Thunderbird before 91.10 are affected, while Thunderbird disables scripting when reading email.

CVSS severity8.8
High
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect WASM assembly generation in affected Mozilla Firefox and Thunderbird releases allows remote attackers to crash arm64 clients. The arm64 JIT lowering for f32.copysign treats the second operand as start-only while reusing the first operand's register, allowing output to clobber a live input and violate allocation integrity. A victim must process attacker-controlled WASM on an arm64 build; Firefox before 101, Firefox ESR before 91.10, and Thunderbird before 91.10 are affected, while Thunderbird disables scripting when reading email.

The record

CVE
CVE-2022-31740
Published
Dec 22, 2022
Updated
Apr 16, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-119, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 22, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 16, 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 <101

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <101
Mozilla · Thunderbirdversion=unspecified <91.10
Mozilla · Firefox ESRversion=unspecified <91.10

Published CVSS scores

8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
8.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:R/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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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-119Improper Restriction of Operations within the Bounds of a Memory Buffer
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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