CVE-2026-72522: libexpat before 2.8.3 has an out-of-bounds read and resultant infinite loop because low surrogates are treated the same as high surrogates during Unicode processing in the *_toUtf16 functions.

mediumCVSS 6.2CVE-2026-72522

CSIRTS triage

vendor: libexpat product: libexpat Memory corruption Denial of serviceaffected: before 2.8.3

What: An out-of-bounds read and infinite loop occurs in Unicode processing functions because low surrogates are incorrectly treated as high surrogates.
Who is affected: Applications using libexpat before version 2.8.3 to parse XML with certain Unicode sequences.
Urgency: Medium severity with CVSS 6.2; no exploitation reported but can cause denial of service through infinite loops.
Action: Upgrade libexpat to version 2.8.3 or later.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 6.2
Published: 2026-08-11
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-72522

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-725220.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 7% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-72522	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

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Recent advisories for libexpat

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

mediumCVE-2026-72522: libexpat before 2.8.3 has an out-of-bounds read and resultant infinite loop because low surrog…nvd · 2026-08-10
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