CVE-2017-3737: Debian Linux

Medium severity, CVSS 5.9. EPSS: 78.7% chance of exploitation in the next 30 days.

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.

Affected products

• Debian Debian Linux: version 9.0 only
• OpenSSL OpenSSL: version 1.0.2b only; version 1.0.2c only; version 1.0.2d only; version 1.0.2e only; version 1.0.2f only; version 1.0.2g only; …

Published 2017-12-07. Last modified 2026-06-17.