Modgnutls is a TLS module for Apache HTTPD based on GnuTLS. In versions prior to 0.12.3 and 0.13.0, code for client certificate verification imported the certificate chain sent by the client into a fixed size gnutlsx509crtt x509[] array without checking the number of certificates is less than or equal to the array size. gnutlsx509crtt is a typedef for a pointer to an opaque GnuTLS structure created using with gnutlsx509crtinit() before importing certificate data into it, so no attacker-controlled data was written into the stack buffer, but writing a pointer after the last array element generally triggered a segfault, and could theoretically cause stack corruption otherwise (not observed in practice). Server configurations that do not use client certificates (GnuTLSClientVerify ignore, the default) are not affected. The problem has been fixed in version 0.12.3 by checking the length of the provided certificate chain and rejecting it if it exceeds the buffer length, and in version 0.13.0 by rewriting certificate verification to use gnutlscertificateverifypeers(), removing the need for the buffer entirely. There is no workaround. Version 0.12.3 provides the minimal fix for users of 0.12.x who do not wish to upgrade to 0.13.0 yet.

It was reported that under certain conditions modgnutls ignores "GnuTLSClientVerify require" when specified in directory [1] and server [2] context. Suggested commit that fixes [2] is: https://github.com/airtower-luna/modgnutls/commit/5a8a32bbfb8a83fe6358c5c31c443325a7775fc2 Patch for [1] is attaced in the corresponding bugreport.

[1]: http://issues.outoforder.cc/view.php?id=93 [2]: https://bugs.debian.org/578663

Modgnutls is a TLS module for Apache HTTPD based on GnuTLS. Versions from 0.9.0 to 0.12.0 (including) did not properly fail blocking read operations on TLS connections when the transport hit timeouts. Instead it entered an endless loop retrying the read operation, consuming CPU resources. This could be exploited for denial of service attacks. If trace level logging was enabled, it would also produce an excessive amount of log output during the loop, consuming disk space. The problem has been fixed in commit d7eec4e598158ab6a98bf505354e84352f9715ec, please update to version 0.12.1. There are no workarounds, users who cannot update should apply the errno fix detailed in the security advisory.

Modgnutls is a TLS module for Apache HTTPD based on GnuTLS. Prior to version 0.13.0, code for client certificate verification did not check the key purpose as set in the Extended Key Usage extension. An attacker with access to the private key for a valid certificate issued by a CA trusted for TLS client authentication but designated for a different purpose could have used that certificate to improperly access resources requiring TLS client authentication. Server configurations that do not use client certificates (GnuTLSClientVerify ignore, the default) are not affected. The problem has been fixed in version 0.13.0 by rewriting certificate verification to use gnutlscertificateverifypeers(), and requiring key purpose id-kp-clientAuth (also known as tlswwwclient in GnuTLS) by default if the Extended Key Usage extension is present. The new GnuTLSClientKeyPurpose option allows overriding the expected key purpose if needed (please see the manual for details). Behavior for certificates without an Extended Key Usage extension is unchanged. If dedicated (sub-)CAs are used for issuing TLS client certificates only (not for any other purposes) the issue has no practical impact.