CVE-2026-43820 Memory corruption in swift-nio-ssl
Out-of-bounds memory access in swift-nio-ssl allows attackers to potentially execute code or cause denial of service via crafted SSL certificates.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-43820?
CVE-2026-43820 is a high-severity memory corruption vulnerability in Apple swift-nio-ssl, published on 23 Jul 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official 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.
Weakness: CWE-125
Which versions are affected by CVE-2026-43820?
It affects 1 product.
Products include Apple Swiftnio Ssl.
How do I fix CVE-2026-43820?
No fix has been published for CVE-2026-43820 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-43820 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43820 exists.
Other vulnerabilities in Apple swift-nio-ssl
Sources
Also known as GHSA-xfxg-9975-pc2j.