pam-krb5 before 4.9 has a buffer overflow that might cause remote code execution in situations involving supplemental prompting by a Kerberos library. It may overflow a buffer provided by the underlying Kerberos library by a single '\0' byte if an attacker responds to a prompt with an answer of a carefully chosen length. The effect may range from heap corruption to stack corruption depending on the structure of the underlying Kerberos library, with unknown effects but possibly including code execution. This code path is not used for normal authentication, but only when the Kerberos library does supplemental prompting, such as with PKINIT or when using the non-standard no_prompt PAM configuration option.
The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer, leading to a buffer overflow.
| Link | Tags |
|---|---|
| https://github.com/rra/pam-krb5/commit/e7879e27a37119fad4faf133a9f70bdcdc75d760 | third party advisory patch |
| http://www.openwall.com/lists/oss-security/2020/03/31/1 | patch mailing list third party advisory |
| https://www.debian.org/security/2020/dsa-4648 | third party advisory vendor advisory |
| https://lists.debian.org/debian-lts-announce/2020/04/msg00000.html | third party advisory mailing list |
| https://usn.ubuntu.com/4314-1/ | vendor advisory |
| https://www.eyrie.org/~eagle/software/pam-krb5/security/2020-03-30.html |