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Improper Restriction of Operations within the Bounds of a Memory Buffer


Severity High
Score 7.5/10


The "big2_toUtf8" function in 'lib/xmltok.c' in 'libexpat' in Expat 2.0.1, as used in the XML-Twig module for Perl, allows context-dependent attackers to cause a Denial of Service (application crash) via an XML document with malformed UTF-8 sequences that trigger a buffer over-read, related to the "doProlog" function in 'lib/xmlparse.c', a different vulnerability than CVE-2009-2625 and CVE-2009-3720. This issue also affects Apache HTTP Server in versions 2.0.35 through 2.0.63, and 2.2.0 through 2.2.16.

  • LOW
  • NONE
  • NONE
  • NONE
  • NONE
  • HIGH

CWE-119 - Buffer Overflow

Buffer overflow attacks involve data transit and operations exceeding the restricted memory buffer, thereby corrupting or overwriting data in adjacent memory locations. Such overflow allows the attacker to run arbitrary code or manipulate the existing code to cause privilege escalation, data breach, denial of service, system crash and even complete system compromise. Given that languages such as C and C++ lack default safeguards against overwriting or accessing data in their memory, applications utilizing these languages are most susceptible to buffer overflows attacks.

Advisory Timeline

  • Published