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CVE-2026-77214

Status: Awaiting AnalysisHigh (8.3)—

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.

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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.

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

🎯 ATT&CK techniques

How this vulnerability is exploited and what the attacker gains, in MITRE ATT&CK terms.

Vulnerabilidad remota (AV:N, PR:N, UI:N) en libexpat expuesta en aplicaciones web/redes; el over-read de heap discierra información de memoria (punteros, ASLR bypass) sin ejecución de código directa, permitiendo reconocimiento y derrotas defensivas.

Inferred by our analysis agent from the official description, CVSS vector and CWE, and checked by a supervisor. May contain errors.

🛡️ ATT&CK mitigations that cover these techniques

Privileged Account ManagementNetwork SegmentationLimit Access to Resource Over NetworkVulnerability ScanningUser Account ManagementFilter Network Traffic

Affected technologies (1)

⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.

Libexpat — LibexpatAI

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2026-77214",
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    }
  ],
  "lastModified": "2026-10-10T03:17:08.487",
  "sourceIdentifier": "disclosure@vulncheck.com"
}