DescriptionA buffer overflow was discovered in libxml2 20904-GITv2.9.4-16-g0741801. The function xmlSnprintfElementContent in valid.c is supposed to recursively dump the element content definition into a char buffer 'buf' of size 'size'. The variable len is assigned strlen(buf). If the content->type is XML_ELEMENT_CONTENT_ELEMENT, then (i) the content->prefix is appended to buf (if it actually fits) whereupon (ii) content->name is written to the buffer. However, the check for whether the content->name actually fits also uses 'len' rather than the updated buffer length strlen(buf). This allows us to write about "size" many bytes beyond the allocated memory. This vulnerability causes programs that use libxml2, such as PHP, to crash.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SuSE, Mageia, GitHub code/issues, web search, more)
ReferencesDLA-1008-1, DSA-3952-1
NVD severitymedium (attack range: remote)
Debian Bugs863022

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
libxml2 (PTS)wheezy2.8.0+dfsg1-7+wheezy5vulnerable
wheezy (security)2.8.0+dfsg1-7+wheezy9fixed
jessie (security)2.9.1+dfsg1-5+deb8u5fixed
stretch (security)2.9.4+dfsg1-2.2+deb9u1fixed
buster, sid2.9.4+dfsg1-4fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs

Notes (not public)
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