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Vulnerability record · CVE-2026-43820 · published 23 July 2026

CVE-2026-43820: Apple swiftnio ssl out-of-bounds read vulnerability

Apple · Swiftnio Ssl

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.

7.7 CVSS 3.1 High EPSS 0.11% · top 98.9% CWE-125 · Out-of-bounds read
7.7CVSS 3.1 base score
0.11%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 2 tagged exploit
4 Sep 2026Last modified by NVD

Description

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.

CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/apple/swift-nio-ssl/security/advisories/GHSA-xfxg-9975-pc2j Vendor AdvisoryExploit
https://github.com/apple/swift-nio-ssl/security/advisories/GHSA-xfxg-9975-pc2j Vendor AdvisoryExploit

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-43820), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.