Reference page — cumulative record through Saturday, October 3, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.
AV AC AT PR UI VC VI VA CVSS EPSS %ile KEV N L N N N N H N 8.7 .0040 32.2 —
AFFECTED Product Versions Fixed libexpat unspecified 2.8.5
TIMELINE Sep 19 Reserved by VulnCheck Sep 19 Published (CNA: VulnCheck) Sep 28 PATCH SHIPPED — CVE-2026-93990 (libexpat). Fixed in libexpat 2.8.5.
Expat before 2.8.5 fails to validate that a high surrogate in UTF-16 input is followed by a low surrogate, allowing malformed UTF-16 sequences to be accepted. Attackers can supply UTF-16 encoded XML containing lone high surrogates that consume the following code unit, causing Expat to pass unpaired surrogates to applications built with XML_UNICODE and to silently replace input characters in other builds.
| Date | Event | Detail |
|---|---|---|
| September 19, 2026 | Reserved | Reserved by VulnCheck |
| September 19, 2026 | Published | Published (CNA: VulnCheck) |
| September 28, 2026 | PATCH SHIPPED | PATCH SHIPPED — CVE-2026-93990 (libexpat). Fixed in libexpat 2.8.5. |
| Vendor | Product / Package | Ecosystem | Version introduced | Fixed |
|---|---|---|---|---|
| libexpat | libexpat | — | — | 2.8.5 |
Authoritative record: CVE-2026-93990 at cve.org
Vendors: libexpat
Weaknesses: CWE-176
This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-93990 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Saturday, October 3, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.
