Process crash via undersized WebAssembly return area
Published Jun 24, 2021 · Updated Aug 3, 2024
Incorrect calculation in Mozilla Firefox before 88, Firefox ESR before 78.10, and Thunderbird before 78.10 allows remote attackers to cause a crash. The Ion WebAssembly compiler allocates four bytes for an x86 float32 multi-value return even though the JavaScript-to-WebAssembly conversion writes eight, overwriting the adjacent saved TLS pointer with zero. Exploitation requires an x86-32 build and crafted WebAssembly that returns float32 through JavaScript; the demonstrated consequence is a near-null read and process crash.
Summary
What happened
Incorrect calculation in Mozilla Firefox before 88, Firefox ESR before 78.10, and Thunderbird before 78.10 allows remote attackers to cause a crash. The Ion WebAssembly compiler allocates four bytes for an x86 float32 multi-value return even though the JavaScript-to-WebAssembly conversion writes eight, overwriting the adjacent saved TLS pointer with zero. Exploitation requires an x86-32 build and crafted WebAssembly that returns float32 through JavaScript; the demonstrated consequence is a near-null read and process crash.
The record
- CVE
- CVE-2021-29945
- Published
- Jun 24, 2021
- Updated
- Aug 3, 2024
- Vendor
- Mozilla
- Product
- Firefox
- Classifications
- CWE-682, T1204
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jun 24, 2021CVE publishedPublication date reported by the CVE source.
- Aug 3, 2024Record 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.
- Affected versionversion=unspecified <88
What conditions does exploitation require?
What is affected?
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.
Public exploit references
- Mozilla WebAssembly JIT crash testcaseproof of concept · demonstrated
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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