URL: http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2011-5094 Assigned: 20120616 Reference: URL: http://www.openwall.com/lists/oss-security/2011/07/08/2 Reference: URL: http://www.ietf.org/mail-archive/web/tls/current/msg07564.html Reference: URL: http://www.ietf.org/mail-archive/web/tls/current/msg07567.html Reference: URL: http://www.ietf.org/mail-archive/web/tls/current/msg07553.html Reference: URL: http://www.ietf.org/mail-archive/web/tls/current/msg07576.html Reference: URL: http://www.ietf.org/mail-archive/web/tls/current/msg07577.html Reference: MISC: http://orchilles.com/2011/03/ssl-renegotiation-dos.html Reference: MISC: http://vincent.bernat.im/en/blog/2011-ssl-dos-mitigation.html Reference: MISC: http://www.educatedguesswork.org/2011/10/ssltls_and_computational_dos.html Reference: MISC: https://bugzilla.redhat.com/show_bug.cgi?id=707065 ** DISPUTED ** Mozilla Network Security Services (NSS) 3.x, with certain settings of the SSL_ENABLE_RENEGOTIATION option, does not properly restrict client-initiated renegotiation within the SSL and TLS protocols, which might make it easier for remote attackers to cause a denial of service (CPU consumption) by performing many renegotiations within a single connection, a different vulnerability than CVE-2011-1473. NOTE: it can also be argued that it is the responsibility of server deployments, not a security library, to prevent or limit renegotiation when it is inappropriate within a specific environment. NOTE: this was originally tracked in bug #707065.
As noted in bug 707065, comment 2, applications using NSS can easily instruct the library to refuse any SSL/TLS session renegotiation if such functionality is not needed using the SSL_ENABLE_RENEGOTIATION option value SSL_RENEGOTIATE_NEVER. Setting NSS_SSL_ENABLE_RENEGOTIATION environment variable to value of 0 or n should mitigate this issue without modifying application, unless the application explicitly sets the SSL_ENABLE_RENEGOTIATION option. I filed upstream bug as there was none yet. It's quite likely upstream will decide to wontfix given the nature of this issue and available mitigation. https://bugzilla.mozilla.org/show_bug.cgi?id=780846
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2011-5094