CVE-2024-9403Public exploitNetwork attack vector

Arbitrary code execution via misaligned WebAssembly calls

Published Oct 1, 2024 · Updated Mar 19, 2025

Memory corruption in Mozilla Firefox and Thunderbird before 131 allows remote attackers to execute arbitrary code through WebAssembly content. The JIT-to-WebAssembly entry stub places an ExitFooterFrame in the padded parameter area, and tail-call setup overwrites its frame type, corrupting frame iteration after a trap. Exploitation requires WebAssembly tail calls and complex JIT tiering; Thunderbird mail reading disables scripting, limiting exposure to browser-like contexts.

CVSS severity7.3
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

Memory corruption in Mozilla Firefox and Thunderbird before 131 allows remote attackers to execute arbitrary code through WebAssembly content. The JIT-to-WebAssembly entry stub places an ExitFooterFrame in the padded parameter area, and tail-call setup overwrites its frame type, corrupting frame iteration after a trap. Exploitation requires WebAssembly tail calls and complex JIT tiering; Thunderbird mail reading disables scripting, limiting exposure to browser-like contexts.

The record

CVE
CVE-2024-9403
Published
Oct 1, 2024
Updated
Mar 19, 2025
Vendor
Mozilla
Product
Firefox
Classifications
CWE-119, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 1, 2024CVE publishedPublication date reported by the CVE source.
  2. Mar 19, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=0 <131
  2. Affected versionversion=unspecified <131

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=0 <131; version=unspecified <131
Mozilla · Thunderbirdversion=0 <131; version=unspecified <131

Published CVSS scores

7.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/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.

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

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

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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