Out-of-bounds read in HTTP client no_proxy handling

Vulnerability Description

Issue summary: An application using the OpenSSL HTTP client API functions may trigger an out-of-bounds read if the 'no_proxy' environment variable is set and the host portion of the authority component of the HTTP URL is an IPv6 address. Impact summary: An out-of-bounds read can trigger a crash which leads to Denial of Service for an application. The OpenSSL HTTP client API functions can be used directly by applications but they are also used by the OCSP client functions and CMP (Certificate Management Protocol) client implementation in OpenSSL. However the URLs used by these implementations are unlikely to be controlled by an attacker. In this vulnerable code the out of bounds read can only trigger a crash. Furthermore the vulnerability requires an attacker-controlled URL to be passed from an application to the OpenSSL function and the user has to have a 'no_proxy' environment variable set. For the aforementioned reasons the issue was assessed as Low severity. The vulnerable code was introduced in the following patch releases: 3.0.16, 3.1.8, 3.2.4, 3.3.3, 3.4.0 and 3.5.0. The FIPS modules in 3.5, 3.4, 3.3, 3.2, 3.1 and 3.0 are not affected by this issue, as the HTTP client implementation is outside the OpenSSL FIPS module boundary.

References

• https://openssl-library.org/news/secadv/20250930.txt
• https://github.com/openssl/openssl/commit/2b4ec20e47959170422922eaff25346d362dcb35
• https://github.com/openssl/openssl/commit/7cf21a30513c9e43c4bc3836c237cf086e194af3
• https://github.com/openssl/openssl/commit/bbf38c034cdabd0a13330abcc4855c866f53d2e0
• https://github.com/openssl/openssl/commit/89e790ac431125a4849992858490bed6b225eadf
• https://github.com/openssl/openssl/commit/654dc11d23468a74fc8ea4672b702dd3feb7be4b