Executive brief
OpenSSL's TLS implementation contains a crash vulnerability when configured with RFC7250 Raw Public Keys (RPKs) using only a private key without a certificate. When a remote peer sends a specific TLS extension (signature_algorithms_cert), the application crashes due to a NULL pointer dereference. This results in denial of service—affected services become unavailable. No data theft or unauthorized execution is possible.
Technical details
The vulnerability is a NULL pointer dereference (CWE-476) in OpenSSL's TLS 1.3 implementation when handling the RFC7250 Raw Public Key extension. The root cause: servers or clients configured with only a private key (no matching certificate) fail to properly handle the "signature_algorithms_cert" TLS extension sent by a remote peer. When a remote peer solicits raw public keys and sends this extension, the code attempts to dereference a NULL pointer, causing the application to abort. The attack is network-reachable and requires no authentication or user interaction—a malicious peer can trigger the crash by sending a crafted TLS handshake. The impact is denial of service only (application crash); no data disclosure or code execution is possible. Patches are available in recent OpenSSL releases.
Affected products
- OpenSSL OpenSSL <UNKNOWN>
Timeline
- 2026-08-25: disclosed
- 2026-08-24: patched: Fixes merged in upstream OpenSSL