OpenSSL 1.0.2 (starting from version 1.0.2b) introduced an "error state" mechanism. The intent was that if a fatal error occurred during a handshake then OpenSSL would move into the error state and would immediately fail if you attempted to continue the handshake. This works as designed for the explicit handshake functions (SSL_do_handshake(), SSL_accept() and SSL_connect()), however due to a bug it does not work correctly if SSL_read() or SSL_write() is called directly. In that scenario, if the handshake fails then a fatal error will be returned in the initial function call. If SSL_read()/SSL_write() is subsequently called by the application for the same SSL object then it will succeed and the data is passed without being decrypted/encrypted directly from the SSL/TLS record layer. In order to exploit this issue an application bug would have to be present that resulted in a call to SSL_read()/SSL_write() being issued after having already received a fatal error. OpenSSL version 1.0.2b-1.0.2m are affected. Fixed in OpenSSL 1.0.2n. OpenSSL 1.1.0 is not affected.
2017-12-07T16:29:00.193
2025-04-20T01:37:25.860
Deferred
CVSSv3.0: 5.9 (MEDIUM)
AV:N/AC:M/Au:N/C:P/I:N/A:N
8.6
2.9
| Type | Vendor | Product | Version/Range | Vulnerable? |
|---|---|---|---|---|
| Application | openssl | openssl | 1.0.2b | Yes |
| Application | openssl | openssl | 1.0.2c | Yes |
| Application | openssl | openssl | 1.0.2d | Yes |
| Application | openssl | openssl | 1.0.2e | Yes |
| Application | openssl | openssl | 1.0.2f | Yes |
| Application | openssl | openssl | 1.0.2g | Yes |
| Application | openssl | openssl | 1.0.2h | Yes |
| Application | openssl | openssl | 1.0.2i | Yes |
| Application | openssl | openssl | 1.0.2j | Yes |
| Application | openssl | openssl | 1.0.2k | Yes |
| Application | openssl | openssl | 1.0.2l | Yes |
| Application | openssl | openssl | 1.0.2m | Yes |
| Operating System | debian | debian_linux | 9.0 | Yes |