Denial of service via unchecked certificate length
Published Nov 24, 2025 · Updated Nov 24, 2025
Denial of service in OISM libcoap 4.3.5 allows remote attackers to crash TLS-enabled processes with a crafted TLS certificate. During certificate verification, tls_verify_call_back() passes the -1 error returned by i2d_X509() to malloc() as an unsigned allocation size instead of rejecting the certificate. The attack is unauthenticated but requires an OpenSSL-backed TLS or DTLS endpoint to process the malicious certificate; the resulting allocation failure terminates the affected process.
Summary
What happened
Denial of service in OISM libcoap 4.3.5 allows remote attackers to crash TLS-enabled processes with a crafted TLS certificate. During certificate verification, tls_verify_call_back() passes the -1 error returned by i2d_X509() to malloc() as an unsigned allocation size instead of rejecting the certificate. The attack is unauthenticated but requires an OpenSSL-backed TLS or DTLS endpoint to process the malicious certificate; the resulting allocation failure terminates the affected process.
The record
- CVE
- CVE-2025-65495
- Published
- Nov 24, 2025
- Updated
- Nov 24, 2025
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-195, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Nov 24, 2025CVE publishedPublication date reported by the CVE source.
- Nov 24, 2025Record updatedLatest update available in the CVE record.
Exploitability
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Attacks
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