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CWE-789Weakness · CWE-789

CVE-2026-59646

HIGH · 8.7 CVSS v4.0 Published 2026-08-03
Patch available
A vendor patch is available. No clean upgrade release — apply the published patch.
See remediation →
96/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click Patch available 3 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In Bouncy Castle for Java before 1.85, DTLS handshake reassembler allocates buffer from unchecked 24-bit length. This issue also affects Bouncy Castle for Java LTS before 2.73.12, and Bouncy Castle for Java FIPS (BC-FJA) before bctls-fips 1.0.24 (1.0.X series), 2.0.24 (2.0.X series) and 2.1.24 (2.1.X series).

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · moderate confidence

The DTLS handshake reassembler in Bouncy Castle for Java fails to validate a 24-bit length field before allocating buffers, potentially allowing an attacker to trigger excessive memory allocation or buffer overflow conditions via specially crafted DTLS handshake messages.

MitigationUpgrade Bouncy Castle for Java to version 1.85 or later (LTS to 2.73.12 or later), or BC-FIPS to bctls-fips 1.0.24/2.0.24/2.1.24 or later. If immediate upgrade is not possible, consider restricting DTLS connectivity or implementing network-level filtering.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
Authentication
X
User interaction
None
Scope
X

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Bouncy Castle Java library presence
    Search for bcprov-*.jar or bcutil-*.jar files in your application classpath, lib directories, or dependency manifests (pom.xml, build.gradle). Use: find . -name 'bcprov*.jar' -o -name 'bcutil*.jar'
    Affected if Bouncy Castle Java library is present in the environment
  2. Determine installed Bouncy Castle version
    Examine the JAR filename directly (e.g., bcprov-jdk18on-1.76.jar) or inspect the MANIFEST.MF file inside the JAR for the Implementation-Version attribute. In Maven/Gradle, run: mvn dependency:list | grep bouncycastle or gradle dependencies | grep bouncycastle
    Affected if Version is earlier than 1.85, 2.73.12, or BC-FIPS versions earlier than 1.0.24/2.0.24/2.1.24
  3. Verify DTLS protocol usage
    Search codebase for DTLS-related imports (org.bouncycastle.*.dtls) and configuration classes such as DTLSClient, DTLSServer, DTLSTransport, or DTLSReassembler. Review network configuration files for DTLS-enabled ports (typically 443/DTLS, 4434, or custom DTLS ports)
    Affected if Application uses DTLS handshake processing or has DTLS server/client functionality enabled
  4. Check for exposed DTLS endpoints
    Inspect server configuration for DTLS listeners. Look for SSLContext or KeyStore configurations using Bouncy Castle providers (BC) with DTLS parameter specifications. Review firewall/network rules for open DTLS-capable ports
    Affected if DTLS endpoints are listening and accessible to network traffic

Environment is affected if Bouncy Castle Java version is below 1.85/2.73.12/(appropriate BC-FIPS version) AND DTLS handshake processing is actively used or exposed

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Patch available Apply the vendor patch
Vendor patch github.com →
Interim mitigation

Upgrade Bouncy Castle for Java to version 1.85 or later (LTS to 2.73.12 or later), or BC-FIPS to bctls-fips 1.0.24/2.0.24/2.1.24 or later. If immediate upgrade is not possible, consider restricting DTLS connectivity or implementing network-level filtering.

Recommended fix High confidence

Upgrade to Bouncy Castle Java 1.85+, LTS 2.73.12+, or BC-FIPS bctls-fips 1.0.24+/2.0.24+/2.1.24+ as appropriate

  1. 1. Identify which Bouncy Castle for Java library is in use (org.bouncycastle:bcprov, org.bouncycastle:bctls, or BC-FIPS)
  2. 2. If using non-FIPS Bouncy Castle: Upgrade org.bouncycastle:bcprov-jdk15to18 (or bcprov-jdk15on) to version 1.85 or later, or to LTS version 2.73.12 or later
  3. 3. If using BC-FIPS (Bouncy Castle FIPS): Determine the bctls-fips version series in use (1.0.X, 2.0.X, or 2.1.X)
  4. 4. For BC-FIPS 1.0.X series: Upgrade bctls-fips to version 1.0.24 or later
  5. 5. For BC-FIPS 2.0.X series: Upgrade bctls-fips to version 2.0.24 or later
  6. 6. For BC-FIPS 2.1.X series: Upgrade bctls-fips to version 2.1.24 or later
  7. 7. Update dependency management files (pom.xml, build.gradle, etc.) with the new version
  8. 8. Rebuild and test the application to verify the upgrade does not introduce regressions
Caveat Bouncy Castle major version upgrades may include API changes; review release notes for any breaking changes between current and target versions

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA3.0 h
21.0 hours of engineering $3,680
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-59646 in production — separate from our analysis above.

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What this is

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  • Version or environment caveats, and links to real fixes
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