Out-of-bounds read & write in RFC 3211 KEK Unwrap

Vulnerability Description

Issue summary: An application trying to decrypt CMS messages encrypted using password based encryption can trigger an out-of-bounds read and write. Impact summary: This out-of-bounds read may trigger a crash which leads to Denial of Service for an application. The out-of-bounds write can cause a memory corruption which can have various consequences including a Denial of Service or Execution of attacker-supplied code. Although the consequences of a successful exploit of this vulnerability could be severe, the probability that the attacker would be able to perform it is low. Besides, password based (PWRI) encryption support in CMS messages is very rarely used. For that reason the issue was assessed as Moderate severity according to our Security Policy. 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 CMS implementation is outside the OpenSSL FIPS module boundary.

References

• https://openssl-library.org/news/secadv/20250930.txt
• https://github.com/openssl/openssl/commit/bae259a211ada6315dc50900686daaaaaa55f482
• https://github.com/openssl/openssl/commit/9e91358f365dee6c446dcdcdb01c04d2743fd280
• https://github.com/openssl/openssl/commit/5965ea5dd6960f36d8b7f74f8eac67a8eb8f2b45
• https://github.com/openssl/openssl/commit/b5282d677551afda7d20e9c00e09561b547b2dfd
• https://github.com/openssl/openssl/commit/a79c4ce559c6a3a8fd4109e9f33c1185d5bf2def
• https://github.openssl.org/openssl/extended-releases/commit/dfbaf161d8dafc1132dd88cd48ad990ed9b4c8ba
• https://github.openssl.org/openssl/extended-releases/commit/c2b96348bfa662f25f4fabf81958ae822063dae3