Heap memory disclosure via unchecked parse length
Published Oct 7, 2026 · Updated Oct 7, 2026
Out-of-bounds read in Expat Project libexpat 2.8.5 and earlier allows attackers to read adjacent heap memory via XML_ParseBuffer. In xmlparse.c, XML_ParseBuffer adds a caller-supplied length to m_bufferEnd without checking the remaining allocation, allowing subsequent parsing to read beyond the heap buffer. The path requires an existing parse buffer and an application that passes an excessive length; network exposure depends on that application's handling of untrusted input.
Summary
What happened
Out-of-bounds read in Expat Project libexpat 2.8.5 and earlier allows attackers to read adjacent heap memory via XML_ParseBuffer. In xmlparse.c, XML_ParseBuffer adds a caller-supplied length to m_bufferEnd without checking the remaining allocation, allowing subsequent parsing to read beyond the heap buffer. The path requires an existing parse buffer and an application that passes an excessive length; network exposure depends on that application's handling of untrusted input.
The record
- CVE
- CVE-2026-77214
- Published
- Oct 7, 2026
- Updated
- Oct 7, 2026
- Vendor
- libexpat Project
- Product
- libexpat
- Classifications
- CWE-125
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Oct 7, 2026CVE publishedPublication date reported by the CVE source.
- Oct 7, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <=2.8.5
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Activity data is delayed. The latest report is Sep 28, 2026.
Weakness, pattern, technique
Public exploit references
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Technologies
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