CVE-2017-3737
Description
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.
How to fix
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| openssl openssl | 1.0.2b, 1.0.2c, 1.0.2d, 1.0.2e, 1.0.2f, 1.0.2g, 1.0.2h, 1.0.2i, 1.0.2j, 1.0.2k, 1.0.2l, 1.0.2m | — |
| debian debian_linux | 9.0 | — |
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