libssh - several

Multiple vulnerabilities were discovered in libssh by Florian Weimer and Xi
Wang:

• CVE-2012-4559:
  multiple double free() flaws
• CVE-2012-4561:
  multiple invalid free() flaws
• CVE-2012-4562:
  multiple improper overflow checks

Those could lead to a denial of service by making an SSH client linked to
libssh crash, and maybe even arbitrary code execution.

For the stable distribution (squeeze), these problems have been fixed in
version 0.4.5-3+squeeze1.

For the testing distribution (wheezy), these problems have been fixed in
version 0.5.3-1.

For the unstable distribution (sid), these problems have been fixed in
version 0.5.3-1.

We recommend that you upgrade your libssh packages.