libexpat through 2.9.0 Denial of Service via Billion Laughs Detection Delay

Summary

libexpat through 2.9.0 contains a denial of service vulnerability because billion laughs protection in accountingDiffTolerated() in xmlparse.c detects entity amplification too late. Attackers can supply a moderately sized XML document with a large DTD and nested entity expansions to consume tens of seconds of CPU per parse.

Remediation

1. Inventory every Libexpat Project Libexpat deployment, including staging.
2. No fixed version appears in the public sources yet. Check the references below and the vendor directly.

References

• Patchhttps://github.com/hannob/lololol
• Patchhttps://github.com/libexpat/libexpat/pull/1433
• Patchhttps://www.vulncheck.com/advisories/libexpat-through-2.9.0-denial-of-service-via-billion-laughs-detection-delay
• Advisoryhttps://github.com/libexpat/libexpat/issues/1160
• Referencehttps://github.com/libexpat/libexpat