CVE-2026-43820 Details
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.
A vulnerability in the handling of subject alternative names (SANs) in Apple Swift NIO SSL versions 2.18.0 through 2.37.1 can lead to out-of-bounds memory access. The issue arises because the NIOSSLCertificate._subjectAlternativeNames method provides raw byte access to a certificate's SANs. NIOSSL assumes that the SANs are backed by ASN1_STRING, but this is not the case for all SAN types. As a result, accessing the buffer for certain non-string SAN types can cause memory access violations.
Users should upgrade to Swift NIO SSL version 2.37.2 or later, or modify their code to check the type of each subject alternative name before accessing the raw bytes.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed Jul 24, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/apple/swift-nio-ssl/security/advisories/GHSA-xfxg-9975-pc2j | CISA-ADP | Vendor AdvisoryExploit |
| https://github.com/apple/swift-nio-ssl/security/advisories/GHSA-xfxg-9975-pc2j | [email protected] | Vendor AdvisoryExploit |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-125 | Out-of-bounds Read | CISA-ADP |
Affected Products
| Product | Versions |
|---|---|
| apple swiftnio ssl | >= 2.18.0, < 2.37.2 |
CPE
Remediation
| |
Change History
3 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Sep 4, 2026 | Initial Analysis | [email protected] |
| Jul 24, 2026 | CVE Modified | CISA-ADP |
| Jul 23, 2026 | New CVE Received | [email protected] |