Out-of-bounds Read in Apple Swift-Nio-Ssl
CVE-2026-43820
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.
Vulnerability class: Buffer Overflow
EPSS: 0.001 (1.4th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.7 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H.
Affected products
- Apple Swift-nio-ssl — versions 0
- Apple Swiftnio_ssl
Weakness classification (CWE)
References
- product-security@apple.com (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-43820?
- CVE-2026-43820 is a high-severity vulnerability in Apple Swift-Nio-Ssl, classified under Out-of-bounds Read. CVSS score: 7.7/10. Published 2026-07-23.
- How severe is CVE-2026-43820?
- High severity. CVSS v3 base score is 7.7 out of 10.