UBUNTU-CVE-2026-95691: Use After Free
Issue summary: A retransmitted QUIC CRYPTO frame can release packet storage while the TLS record layer retains a direct pointer into that storage causing use after free. Impact summary: A malicious QUIC server can cause a heap-use-after-free read in the OpenSSL QUIC client. The server can also identify one allocator-adjacent byte through the client's protected Handshake response. CWE: CWE-416: Use After Free Description: During CRYPTO stream processing, a pointer into the first frame's memory on the stream is lent to the TLS handshake processing. The memory must remain stable until it is processed and released. However the processing of retransmitted CRYPTO frames could release the memory if the retransmitted frame fully overlapped the existing frame. This then causes use-after-free read when the TLS handshake processing continues. The use-after-free read can lead to a Denial-of-Service of the client application or a minor leak of information about the heap memory contents that might be overwritten with other data, subsequently allocated by the application, to the peer. FIPS impact: no The FIPS module is not affected as the QUIC implementation is outside of the OpenSSL FIPS module boundary.
Affected Software
Event History
Frequently Asked Questions
Which deployments are exposed?
OpenSSL applications using the QUIC client and connecting to a malicious QUIC server are exposed. The issue occurs during QUIC CRYPTO stream processing.
What must an attacker be able to do?
An attacker must operate or control a QUIC server that the affected client connects to. The server can send retransmitted CRYPTO frames that fully overlap an existing frame.
Is the OpenSSL FIPS module affected?
No. The QUIC implementation is outside the OpenSSL FIPS module, so the FIPS module is not affected.