Bug 2506497 (CVE-2026-43820)

Summary: CVE-2026-43820 swift-nio-ssl: swift-nio-ssl: Out-of-bounds memory access due to improper handling of Subject Alternative Names
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: high Docs Contact:
Priority: high    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in swift-nio-ssl. This vulnerability arises from the improper handling of Subject Alternative Names (SANs) within SSL certificates. When processing SANs that are not backed by an ASN1_STRING, the system attempts to access memory outside of its allocated buffer, leading to an out-of-bounds memory access. This could allow a remote attacker to cause a denial of service or potentially disclose sensitive information.
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Description OSIDB Bzimport 2026-07-23 15:02:14 UTC 
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.