CVE-2026-41676: rust-openssl_project rust-openssl Incorrect Calculation of Buffer Size

Vulnerability summary

CVE-2026-41676 is a high (CVSS 7.5) Incorrect Calculation of Buffer Size vulnerability in rust-openssl_project rust-openssl. EPSS estimates a 0.29% chance of exploitation in the next 30 days, higher than 19.7% of scored vulnerabilities.

Timeline

1. 24-04-2026
   PublishedVulnerability first disclosed.
2. 24-04-2026
   Last modifiedVulnerability information updated.

Description

rust-openssl provides OpenSSL bindings for the Rust programming language. From 0.9.27 to before 0.10.78, Deriver::derive (and PkeyCtxRef::derive) sets len = buf.len() and passes it as the in/out length to EVP_PKEY_derive, relying on OpenSSL to honor it. On OpenSSL 1.1.x, X25519, X448, DH and HKDF-extract ignore the incoming *keylen, unconditionally writing the full shared secret (32/56/prime-size bytes). A caller passing a short slice gets a heap/stack overflow from safe code. OpenSSL 3.x providers do check, so this only impacts older OpenSSL. This vulnerability is fixed in 0.10.78.

• CWE-131Incorrect Calculation of Buffer SizeThe product does not correctly calculate the size to be used when allocating a buffer, which could lead to a buffer overflow.
• CWE-787Out-of-bounds WriteThe product writes data past the end, or before the beginning, of the intended buffer.