Heap-based buffer underflow in the modmul function in sshbn.c in PuTTY before 0.63 allows remote SSH servers to cause a denial of service (crash) and possibly trigger memory corruption or code execution via a crafted DSA signature, which is not properly handled when performing certain bit-shifting operations during modular multiplication.
The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.
| Link | Tags |
|---|---|
| http://www.openwall.com/lists/oss-security/2013/08/06/11 | mailing list |
| http://secunia.com/advisories/54533 | third party advisory |
| http://www.chiark.greenend.org.uk/~sgtatham/putty/wishlist/vuln-modmul.html | vendor advisory |
| http://www.debian.org/security/2013/dsa-2736 | vendor advisory |
| http://lists.opensuse.org/opensuse-updates/2013-08/msg00035.html | vendor advisory |
| http://secunia.com/advisories/54379 | third party advisory vendor advisory |
| http://svn.tartarus.org/sgt/putty/sshbn.c?sortby=date&r1=9977&r2=9976&pathrev=9977 | patch |