OpenSSL 1.0.1g NULL Pointer Dereference

2014.06.06
Credit: Dr Stephen
Risk: Medium
Local: No
Remote: Yes
CWE: CWE-310


CVSS Base Score: 4.3/10
Impact Subscore: 2.9/10
Exploitability Subscore: 8.6/10
Exploit range: Remote
Attack complexity: Medium
Authentication: No required
Confidentiality impact: None
Integrity impact: None
Availability impact: Partial

The ssl3_send_client_key_exchange function in s3_clnt.c in OpenSSL before 0.9.8za, 1.0.0 before 1.0.0m, and 1.0.1 before 1.0.1h, when an anonymous ECDH cipher suite is used, allows remote attackers to cause a denial of service (NULL pointer dereference and client crash) by triggering a NULL certificate value. diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c index c99a4c4..0457af8 100644 (file) --- a/ssl/s3_clnt.c +++ b/ssl/s3_clnt.c @@ -2512,6 +2512,13 @@ int ssl3_send_client_key_exchange(SSL *s) int ecdh_clnt_cert = 0; int field_size = 0; + if (s->session->sess_cert == NULL) + { + ssl3_send_alert(s,SSL3_AL_FATAL,SSL_AD_UNEXPECTED_MESSAGE); + SSLerr(SSL_F_SSL3_SEND_CLIENT_KEY_EXCHANGE,SSL_R_UNEXPECTED_MESSAGE); + goto err; + } + /* Did we send out the client's * ECDH share for use in premaster * computation as part of client certificate?

References:

https://git.openssl.org/gitweb/?p=openssl.git;a=commit;h=8011cd56e39a433b1837465259a9bd24a38727fb


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