It was discovered that Expat incorrectly handled certain files. An attacker could possibly use this issue to cause a crash or execute arbitrary code.

Gustavo Grieco discovered that Expat incorrectly handled malformed XML data. If a user or application linked against Expat were tricked into opening a crafted XML file, an attacker could cause a denial of service, or possibly execute arbitrary code. (CVE-2016-0718)

It was discovered that Expat computed hash values without restricting the ability to trigger hash collisions predictably. If a user or application linked against Expat were tricked into opening a crafted XML file, an attacker could cause a denial of service by consuming excessive CPU resources. (CVE-2012-0876) Tim Boddy discovered that Expat did not properly handle memory reallocation when processing XML files. If a user or application linked against Expat were tricked into opening a crafted XML file, an attacker could cause a denial of service by consuming excessive memory resources. This issue only affected Ubuntu 8.04 LTS, 10.04 LTS, 11.04 and 11.10. (CVE-2012-1148)