Code execution via oversized S/MIME signature copy
Published Feb 16, 2023 · Updated Mar 19, 2025
Heap overflow in Mozilla Thunderbird before 91.3.0 allows remote attackers to execute code via a crafted S/MIME message. During signature verification, NSS vfy_CreateContext copies an attacker-sized DER-encoded DSA or RSA-PSS signature into the fixed-size VFYContext buffer without enforcing its maximum length. Processing the signed message requires no authentication or user interaction, and the overwrite can corrupt adjacent function pointers inside the mail client.
Summary
What happened
Heap overflow in Mozilla Thunderbird before 91.3.0 allows remote attackers to execute code via a crafted S/MIME message. During signature verification, NSS vfy_CreateContext copies an attacker-sized DER-encoded DSA or RSA-PSS signature into the fixed-size VFYContext buffer without enforcing its maximum length. Processing the signed message requires no authentication or user interaction, and the overwrite can corrupt adjacent function pointers inside the mail client.
The record
- CVE
- CVE-2021-43529
- Published
- Feb 16, 2023
- Updated
- Mar 19, 2025
- Vendor
- Mozilla
- Product
- Thunderbird
- Classifications
- CWE-787, T1203
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 16, 2023CVE publishedPublication date reported by the CVE source.
- Mar 19, 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.
- Affected versionversion=unspecified <91.3.0
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
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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