CVE-2026-43820: Apple Swiftnio SSL

High severity, CVSS 7.7. EPSS: 0.1% chance of exploitation in the next 30 days.

NIOSSLCertificate._subjectAlternativeNames provides access to the raw bytes for a cert's SANs. NIOSSL provides access to a buffer assumed to be backed by an ASN1_STRING, but not all SANs are backed by ASN1_STRING, so accessing the buffer for such a type can lead to out-of-bounds memory access. This vulnerability is addressed in swift-nio-ssl version 2.37.2.

Affected products

• Apple Swiftnio SSL: from 2.18.0, before 2.37.2 (fixed in 2.37.2)

Published 2026-07-23. Last modified 2026-09-04.