USN-127-1: bzip2 vulnerabilities

17 May 2005

bzip2 vulnerabilities

A security issue affects these releases of Ubuntu and its derivatives:

  • Ubuntu 5.04
  • Ubuntu 4.10

Software Description


Imran Ghory discovered a race condition in the file permission restore code of bunzip2. While a user was decompressing a file, a local attacker with write permissions in the directory of that file could replace the target file with a hard link. This would cause bzip2 to restore the file permissions to the hard link target instead of to the bzip2 output file, which could be exploited to gain read or even write access to files of other users. (CAN-2005-0953)

Specially crafted bzip2 archives caused an infinite loop in the decompressor which resulted in an indefinitively large output file (“decompression bomb”). This could be exploited to a Denial of Service attack due to disk space exhaustion on systems which automatically process user supplied bzip2 compressed files. (CAN-2005-1260)

Update instructions

The problem can be corrected by updating your system to the following package versions:

Ubuntu 5.04
Ubuntu 4.10

To update your system, please follow these instructions: