Published: 08 September 2010

The DNS resolution functionality in the CIFS implementation in the Linux kernel before 2.6.35, when CONFIG_CIFS_DFS_UPCALL is enabled, relies on a user's keyring for the dns_resolver upcall in the cifs.upcall userspace helper, which allows local users to spoof the results of DNS queries and perform arbitrary CIFS mounts via vectors involving an add_key call, related to a "cache stuffing" issue and MS-DFS referrals.

From the Ubuntu security team

David Howells discovered that DNS resolution in CIFS could be spoofed. A local attacker could exploit this to control DNS replies, leading to a loss of privacy and possible privilege escalation.



CVSS 3 base score: 7.8


sbeattie according to oss-security discussion, git commit 6103335de8afa5d780dcd512abe85c696af7b040 introduced the problem, so 2.6.25-rc1 onwards.
smb Jaunty *may* be affected, but the problem is that there is no infra- structure for thread credentials, so even if it is possible to back- port the whole thing it would be completely different and prone to be incorrect. That together with the fact that Jaunty is EOL more or less I don't think we should put in much effort there.