CVE-2025-0343 CVE-2025-0343: Swift ASN.1 can crash when parsing maliciously formed BER/DER

What is CVE-2025-0343?

CVE-2025-0343 is a high-severity denial of service vulnerability in Swift ASN1, published on 15 Jan 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

Swift ASN.1 can be caused to crash when parsing certain BER/DER constructions. This crash is caused by a confusion in the ASN.1 library itself which assumes that certain objects can only be provided in either constructed or primitive forms, and will trigger a preconditionFailure if that constraint isn't met.

Importantly, these constraints are actually required to be true in DER, but that correctness wasn't enforced on the early node parser side so it was incorrect to rely on it later on in decoding, which is what the library did.

These crashes can be triggered when parsing any DER/BER format object. There is no memory-safety issue here: the crash is a graceful one from the Swift runtime. The impact of this is that it can be used as a denial-of-service vector when parsing BER/DER data from unknown sources, e.g. when parsing TLS certificates.

Weakness: CWE-228

Which versions are affected by CVE-2025-0343?

2 open source packages ship an affected version, including github.com/apple/swift-asn1.

How do I fix CVE-2025-0343?

Upgrade github.com/apple/swift-asn1 to 1.3.1 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2025-0343 being exploited?

There is no known exploitation of CVE-2025-0343 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-w8xv-rwgf-4fwh.