Application crash via unchecked token-label copy
Published Jan 26, 2026 · Updated Jan 26, 2026
Stack-based buffer overflow in GnuTLS on affected Red Hat platforms allows local users to crash applications via an oversized PKCS#11 token label. The gnutls_pkcs11_token_init() path in lib/pkcs11_write.c copies strlen(label) bytes into the 32-byte flabel stack buffer without checking its size. Reachability requires a caller that accepts a user-controlled initialization label; the overwrite crashes the process, while code execution depends on process hardening and inherits the caller's context.
Summary
What happened
Stack-based buffer overflow in GnuTLS on affected Red Hat platforms allows local users to crash applications via an oversized PKCS#11 token label. The gnutls_pkcs11_token_init() path in lib/pkcs11_write.c copies strlen(label) bytes into the 32-byte flabel stack buffer without checking its size. Reachability requires a caller that accepts a user-controlled initialization label; the overwrite crashes the process, while code execution depends on process hardening and inherits the caller's context.
The record
- CVE
- CVE-2025-9820
- Published
- Jan 26, 2026
- Updated
- Jan 26, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat Enterprise Linux 6
- Classifications
- CWE-121, T1068
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 26, 2026CVE publishedPublication date reported by the CVE source.
- Jan 26, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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