libexpat Heap Buffer Over-read in xmlparse.c via XML_ParseBuffer

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  "url": "https://www.cve.org/CVERecord?id=CVE-2026-77214",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "libexpat Heap Buffer Over-read in xmlparse.c via XML_ParseBuffer",
    "summary": "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.",
    "evidence": "cve:CVE-2026-77214",
    "products": [
      {
        "name": {
          "value": "libexpat",
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        "fixed_versions": [],
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    "severity": "high",
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      "modified": "2026-10-27T10:14:34.918Z",
      "provider": "cve",
      "references": [
        "https://github.com/libexpat/libexpat/pull/1393",
        "https://github.com/libexpat/libexpat/commit/13c5f63a7f1c52c2feee3b16a1134d4fb68e9ea0",
        "https://www.vulncheck.com/advisories/libexpat-heap-buffer-over-read-in-xmlparse-c-via-xml-parsebuffer"
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  "source_id": "core-cve",
  "document_id": 391752,
  "published_at": "2026-10-07T14:35:42.794+00:00"
}