Service interruption via duplicate DTLS sequence numbers
Published May 18, 2026 · Updated Aug 31, 2026
Undefined behavior in GnuTLS before 3.8.13 allows remote attackers to interrupt DTLS services with duplicate packet sequence numbers. The handshake_compare function in lib/buffers.c returns a nonzero result for equal sequence values, violating qsort's comparator contract while ordering buffered DTLS handshakes. Reachability requires an application using DTLS and a sorting implementation that takes the affected path; modern glibc avoids that path for the small arrays involved.
Summary
What happened
Undefined behavior in GnuTLS before 3.8.13 allows remote attackers to interrupt DTLS services with duplicate packet sequence numbers. The handshake_compare function in lib/buffers.c returns a nonzero result for equal sequence values, violating qsort's comparator contract while ordering buffered DTLS handshakes. Reachability requires an application using DTLS and a sorting implementation that takes the affected path; modern glibc avoids that path for the small arrays involved.
The record
- CVE
- CVE-2026-42009
- Published
- May 18, 2026
- Updated
- Aug 31, 2026
- Vendor
- 389 Directory Server
- Product
- Red Hat OpenShift Container Platform 4.16
- Classifications
- CWE-475, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- May 18, 2026CVE publishedPublication date reported by the CVE source.
- Aug 31, 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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