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CVE-2024-29857: CVE-2024-29857: Denial of Service via Algorithmic Complexity in Bouncy Castle ECC

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CVE-2024-29857: Denial of Service via Algorithmic Complexity in Bouncy Castle ECC

Vulnerability ID: CVE-2024-29857
CVSS Score: 7.5
Published: 2024-05-09

An algorithmic complexity exhaustion vulnerability exists in the Bouncy Castle cryptographic libraries for Java and C# .NET. The vulnerability affects the processing of Elliptic Curve Cryptography (ECC) parameters defined over binary finite fields. Remote attackers can trigger unbounded resource consumption and cause a denial of service (DoS) by supplying specially crafted X.509 certificates with excessively large field degree parameters.

TL;DR

Bouncy Castle (Java < 1.78, C# < 2.3.1) fails to limit the field degree parameter when processing explicit ECC curve parameters over binary fields. This allows remote attackers to trigger an infinite CPU loop via malicious X.509 certificates.

⚠️ Exploit Status: POC

Technical Details

  • CWE ID: CWE-400 / CWE-125
  • Attack Vector: Network (Malicious X.509 Certificate)
  • CVSS v3.1 Score: 7.5
  • EPSS Score: 0.00337 (56.09%)
  • Impact: 100% CPU Exhaustion (Denial of Service)
  • Exploit Status: Proof of Concept (X.509DoSTool)
  • KEV Status: Not Listed

Affected Systems

  • Jenkins
  • Keycloak
  • Logstash
  • Oracle WebLogic Server
  • IBM SPSS Collaboration and Deployment Services
  • Red Hat Enterprise Linux (RHEL)
  • Amazon Linux
  • Cloudera Flow Management
  • Bouncy Castle Java (BC Java): < 1.78 (Fixed in: 1.78)
  • Bouncy Castle Java LTS: < 2.73.6 (Fixed in: 2.73.6)
  • Bouncy Castle FIPS (BC-FJA): < 1.0.2.5 (Fixed in: 1.0.2.5)
  • Bouncy Castle C# .NET: < 2.3.1 (Fixed in: 2.3.1)

Code Analysis

Commit: fee80dd

Java patch moving the boundary check to the foundational buildField method.

Commit: 56daa6e

C# .NET implementation patch restricting maximum field size parameter.

Exploit Details

Mitigation Strategies

  • Upgrade to Bouncy Castle Java 1.78 or 2.73.6 (LTS)
  • Upgrade to Bouncy Castle C# .NET 2.3.1
  • Upgrade Bouncy Castle FIPS to 1.0.2.5
  • Configure Java system property org.bouncycastle.ec.max_f2m_field_size
  • Configure .NET environment variable Org.BouncyCastle.EC.F2m_MaxSize

Remediation Steps:

  1. Audit project dependencies using SCA tools (Snyk, Dependabot) to identify vulnerable Bouncy Castle versions.
  2. Update Maven/Gradle or NuGet package definitions to the patched versions.
  3. If utilizing third-party applications (Jenkins, Keycloak), apply vendor-specific security patches that bundle the updated Bouncy Castle libraries.
  4. Verify the application test suite executes correctly, ensuring no legacy requirements exist for binary curves exceeding 1142 bits.

References

Read the full report for CVE-2024-29857 on our website for more details including interactive diagrams and full exploit analysis.

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