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.
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History
Wed, 07 Oct 2026 14:45:00 +0000
| Type | Values Removed | Values Added |
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| 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. | |
| Title | libexpat Heap Buffer Over-read in xmlparse.c via XML_ParseBuffer | |
| Weaknesses | CWE-125 | |
| References |
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MITRE
Status: PUBLISHED
Assigner: VulnCheck
Published:
Updated: 2026-10-07T14:35:42.794Z
Reserved: 2026-08-20T18:25:46.943Z
Link: CVE-2026-77214
Vulnrichment
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NVD
Status : Received
Published: 2026-10-07T15:17:53.327
Modified: 2026-10-07T15:17:53.327
Link: CVE-2026-77214
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Weaknesses