OpenSSL up to 3.5.9/4.0.3/4.1.0 QUIC use after free

Summaryinfo

A vulnerability marked as critical has been reported in OpenSSL up to 3.5.9/4.0.3/4.1.0. This issue affects some unknown processing of the component QUIC. Performing a manipulation results in use after free. This vulnerability is known as CVE-2026-95691. Remote exploitation of the attack is possible. No exploit is available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in OpenSSL up to 3.5.9/4.0.3/4.1.0. This affects an unknown code of the component QUIC. The manipulation with an unknown input leads to a use after free vulnerability. CWE is classifying the issue as CWE-416. The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory "belongs" to the code that operates on the new pointer. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at openssl-library.org. This vulnerability is uniquely identified as CVE-2026-95691 since 09/22/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 11/11/2026).

Upgrading to version 3.5.10, 4.0.4 or 4.1.1 eliminates this vulnerability.

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Productinfo

Type

• Network Encryption Software

Name

• OpenSSL

Version

• 3.5.0
• 3.5.1
• 3.5.2
• 3.5.3
• 3.5.4
• 3.5.5
• 3.5.6
• 3.5.7
• 3.5.8
• 3.5.9
• 4.0
• 4.0.0
• 4.0.1
• 4.0.2
• 4.0.3
• 4.1.0

License

• open-source

Website

• Product: https://www.openssl.org/

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