The png_check_keyword function in pngwutil.c in libpng before 1.0.42, and 1.2.x before 1.2.34, might allow context-dependent attackers to set the value of an arbitrary memory location to zero via vectors involving creation of crafted PNG files with keywords, related to an implicit cast of the '\0' character constant to a NULL pointer. NOTE: some sources incorrectly report this as a double free vulnerability.
CVSS Severity (version 2.0):
Impact Subscore: 2.9
Exploitability Subscore: 10.0
CVSS Version 2 Metrics:
Access Vector: Network exploitable
Access Complexity: Low
Authentication: Not required to exploit
Impact Type: Allows unauthorized modification
Official Statement from Red Hat (02/11/2009)
Red Hat does not consider this bug to be a security issue. For a more detailed explanation, please see the following bug:
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[oss-security] 20090109 libpng non issue
[png-mng-implement] 20081126 Memory overwriting bug in png_check_keyword()