CVE-2026-77214

NameCVE-2026-77214
Descriptionlibexpat before commit 13c5f63 contains a heap buffer over-read vulnerability in xmlparse.c. XML_ParseBuffer advances the parse buffer end with parser->m_bufferEnd += len using a caller-supplied length that is not validated against the allocated buffer size, so repeated XML_ParseBuffer calls move m_bufferEnd past the end of the heap allocation and subsequent parsing reads out of bounds. Reaching this path requires a parse buffer to already be present; otherwise XML_ParseBuffer returns XML_ERROR_NO_BUFFER. A buffer is present after a prior call to XML_GetBuffer, either directly (the common case) or indirectly through a prior XML_Parse call that allocates the buffer internally. The over-read discloses adjacent heap memory to the calling application, recovering heap pointers, libc function pointers, and code pointers sufficient to defeat ASLR and build further exploitation primitives.
SourceCVE (at NVD; CERT, ENISA, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
ReferencesDSA-6566-1
Debian Bugs1150320

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
expat (PTS)bookworm2.5.0-1+deb12u2vulnerable
bookworm (security)2.5.0-1+deb12u4vulnerable
trixie2.8.3-1~deb13u1vulnerable
trixie (security)2.9.0-1~deb13u1fixed
forky, sid2.9.0-1fixed

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
expatsourcetrixie2.9.0-1~deb13u1DSA-6566-1
expatsource(unstable)2.9.0-11150320

Notes

https://github.com/libexpat/libexpat/pull/1393
Fixed by: https://github.com/libexpat/libexpat/commit/4d9b1c499ecb66323260a7274edcf86c5eab0517 (R_2_9_0)

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