CVE-2026-77214: libexpat Out-of-bounds Read

Vulnerability summary

CVE-2026-77214 is a high (CVSS 8.3) Out-of-bounds Read vulnerability in libexpat. EPSS estimates a 0.55% chance of exploitation in the next 30 days, higher than 44.8% of scored vulnerabilities.

Timeline

1. 07-10-2026
   PublishedVulnerability first disclosed.
2. 10-10-2026
   Last modifiedVulnerability information updated.

Description

libexpat 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.

• CWE-125Out-of-bounds ReadThe product reads data past the end, or before the beginning, of the intended buffer.