Memory disclosure via mistyped SAN union access
Published Jul 23, 2026 · Updated Jul 23, 2026
Out-of-bounds read in Apple SwiftNIO SSL 2.18.0 through 2.37.1 allows attackers to read process memory via a crafted certificate. NIOSSLCertificate._subjectAlternativeNames reads the ASN1_STRING member of every BoringSSL GENERAL_NAME union without checking whether the SAN type is string-backed. Only consumers that directly access contents without first checking each SAN type are exposed; NIOSSL's internal callers are unaffected.
Summary
What happened
Out-of-bounds read in Apple SwiftNIO SSL 2.18.0 through 2.37.1 allows attackers to read process memory via a crafted certificate. NIOSSLCertificate._subjectAlternativeNames reads the ASN1_STRING member of every BoringSSL GENERAL_NAME union without checking whether the SAN type is string-backed. Only consumers that directly access contents without first checking each SAN type are exposed; NIOSSL's internal callers are unaffected.
The record
- CVE
- CVE-2026-43820
- Published
- Jul 23, 2026
- Updated
- Jul 23, 2026
- Vendor
- Apple
- Product
- SwiftNIO SSL
- Classifications
- CWE-125
- Attack vector
- local
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 23, 2026CVE publishedPublication date reported by the CVE source.
- Jul 23, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <2.37.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Apple advisory non-string SAN proof of conceptproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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