CVE-2025-0343
📋 TL;DR
Swift ASN.1 library crashes when parsing malformed BER/DER data due to incorrect assumptions about constructed vs primitive forms. This creates a denial-of-service vulnerability affecting any application using this library to parse ASN.1 data from untrusted sources, particularly TLS certificate parsing. The crash is graceful without memory safety issues.
💻 Affected Systems
- Swift ASN.1 library
- Applications using Swift ASN.1 for BER/DER parsing
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Remote attackers can crash services parsing ASN.1 data from untrusted sources, causing complete denial of service for affected applications.
Likely Case
Attackers can disrupt TLS certificate validation or other ASN.1 parsing operations, causing service interruptions for applications accepting external data.
If Mitigated
With input validation and rate limiting, impact is limited to temporary service degradation rather than complete outage.
🎯 Exploit Status
Exploitation requires crafting malformed BER/DER data that violates DER constraints but reaches the vulnerable parsing code path.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check GitHub advisory for specific fixed version
Vendor Advisory: https://github.com/apple/swift-asn1/security/advisories/GHSA-w8xv-rwgf-4fwh
Restart Required: No
Instructions:
1. Update Swift ASN.1 library to patched version. 2. Rebuild and redeploy affected applications. 3. No system restart required for library updates.
🔧 Temporary Workarounds
Input validation for ASN.1 data
allValidate BER/DER data before parsing to ensure it conforms to DER constraints
Rate limit ASN.1 parsing operations
allLimit frequency of ASN.1 parsing from untrusted sources to reduce DoS impact
🧯 If You Can't Patch
- Implement strict input validation for all ASN.1 data from untrusted sources
- Deploy WAF or reverse proxy with rate limiting for services parsing external ASN.1 data
🔍 How to Verify
Check if Vulnerable:
Check if application uses Swift ASN.1 library and parses BER/DER data from untrusted sourcesCheck Version:
Check package manager (Swift Package Manager) for swift-asn1 versionVerify Fix Applied:
Verify Swift ASN.1 library version is updated to patched version and test with malformed ASN.1 data📡 Detection & Monitoring
Log Indicators:
- preconditionFailure crashes in Swift runtime
- ASN.1 parsing errors followed by application crashes
Network Indicators:
- Multiple failed TLS handshakes with malformed certificates
- Unusual volume of ASN.1 data to parsing endpoints
SIEM Query:
search 'preconditionFailure' AND 'ASN' OR 'Swift runtime crash' in application logs