Memory corruption via excess sprintf terminators
Published May 26, 2021 · Updated Nov 3, 2025
Buffer overflow in Caca Labs libcaca's master branch allows local users to corrupt memory by exporting a crafted canvas in troff format. The export_troff function allocates an exact-size output buffer but uses sprintf for fixed text and newlines, so each unused NUL terminator writes beyond the accounted output. Triggering the flaw requires a process to import attacker-controlled canvas data and request troff export; the demonstrated result is an AddressSanitizer abort.
Summary
What happened
Buffer overflow in Caca Labs libcaca's master branch allows local users to corrupt memory by exporting a crafted canvas in troff format. The export_troff function allocates an exact-size output buffer but uses sprintf for fixed text and newlines, so each unused NUL terminator writes beyond the accounted output. Triggering the flaw requires a process to import attacker-controlled canvas data and request troff export; the demonstrated result is an AddressSanitizer abort.
The record
- CVE
- CVE-2021-30499
- Published
- May 26, 2021
- Updated
- Nov 3, 2025
- Vendor
- Caca Labs
- Product
- libcaca
- Classifications
- CWE-119, CWE-787, T1203
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 26, 2021CVE publishedPublication date reported by the CVE source.
- Nov 3, 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?
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- Affected versionversion=master
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.
Weakness, pattern, technique
Public exploit references
- libcaca export_troff AddressSanitizer reproducerproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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