How severe is CVE-2025-0343?

CVE-2025-0343 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2025-0343?

CVE-2025-0343 affects the following packages: github.com/apple/swift-asn1 (SwiftURL). Ecosystems affected: SwiftURL.

How do I fix CVE-2025-0343?

Update github.com/apple/swift-asn1 to 1.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-0343 is resolved across your whole dependency graph.

How do I detect CVE-2025-0343 in my SwiftURL dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/apple/swift-asn1. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2025-0343 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2025-0343?

O3 pinpoints whether CVE-2025-0343 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Is CVE-2025-0343 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-0343 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What type of vulnerability is CVE-2025-0343?

CVE-2025-0343 is classified as CWE-228 (CWE-228). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-0343 published, and has it been updated?

CVE-2025-0343 was published on January 15, 2025 and was last updated on July 15, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 SwiftURL

CVE-2025-0343

HIGH

CVE-2025-0343 is a high-severity (CVSS 7.5) CWE-228 vulnerability in github.com/apple/swift-asn1. O3 Security confirms whether CVE-2025-0343 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

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

Also known asGHSA-w8xv-rwgf-4fwh

Published

Jan 15, 2025

Updated

Jul 15, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Blast Radius

1 pkg affected

📦github.com/apple/swift-asn1

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects SwiftURL packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦SwiftURL	`github.com/apple/swift-asn1`	all versions	1.3.1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/apple/swift-asn1. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/apple/swift-asn1 to 1.3.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-0343 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2025-0343 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2025-0343. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

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

O3 Security · Impact-Aware SCA

Is CVE-2025-0343 in your dependencies?

O3 detects CVE-2025-0343 across SwiftURL dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

Scan my dependencies How O3 SCA works