CVE-2026-5598: Bouncy Castle BC-JAVA timing channel in FrodoKEM

CVE-2026-5598 · Severity: high · CVSS 4 · Published 2026-04-15

Bouncy Castle is a widely used Java library that provides cryptographic functions for securing data and communications. A vulnerability in its implementation of the FrodoKEM algorithm could allow an attacker to observe the time it takes to perform certain operations to potentially recover sensitive cryptographic keys. This could lead to the unauthorized decryption of private communications or the compromise of protected data.

Technologies: org.bouncycastle:bcprov-jdk14 (Maven), org.bouncycastle:bcprov-jdk15to18 (Maven), org.bouncycastle:bcprov-jdk18on (Maven). Vendors: Legion of the Bouncy Castle, Maven.

Quick answers

Is CVE-2026-5598 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-5598 being exploited in the wild.
How severe is CVE-2026-5598?
High severity, with a CVSS score of 4, published 15 April 2026.
Which products and versions are affected?
Legion of the Bouncy Castle BC-JAVA (bcprov-jdk14) >= 1.81, < 1.81.1; Legion of the Bouncy Castle BC-JAVA (bcprov-jdk15to18) >= 1.71, < 1.80.2; Legion of the Bouncy Castle BC-JAVA (bcprov-jdk18on) >= 1.82, < 1.84; Legion of the Bouncy Castle BC-JAVA core 1.71 to 1.80.1, 1.81, 1.82 to 1.83; and 3 more.
Is there a fix for CVE-2026-5598?
Yes. org.bouncycastle:bcprov-jdk14 (Maven): upgrade to 1.81.1 or later; org.bouncycastle:bcprov-jdk15to18 (Maven): upgrade to 1.80.2 or later; org.bouncycastle:bcprov-jdk18on (Maven): upgrade to 1.84 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-5598 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-5598?
Check whether you run Legion of the Bouncy Castle BC-JAVA (bcprov-jdk14), Legion of the Bouncy Castle BC-JAVA (bcprov-jdk15to18), Legion of the Bouncy Castle BC-JAVA (bcprov-jdk18on) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • org.bouncycastle:bcprov-jdk14 (Maven): upgrade to 1.81.1 or later
    # set org.bouncycastle:bcprov-jdk14 to 1.81.1 in your pom.xml or build.gradle
  • org.bouncycastle:bcprov-jdk15to18 (Maven): upgrade to 1.80.2 or later
    # set org.bouncycastle:bcprov-jdk15to18 to 1.80.2 in your pom.xml or build.gradle
  • org.bouncycastle:bcprov-jdk18on (Maven): upgrade to 1.84 or later
    # set org.bouncycastle:bcprov-jdk18on to 1.84 in your pom.xml or build.gradle

Technical details

A covert timing channel vulnerability (CWE-385) exists in the Bouncy Castle Java (BC-JAVA) library within the FrodoEngine.java component. The flaw is specifically located in the FrodoKEM algorithm's decryption of encapsulations, where variations in processing time can leak information about the underlying cryptographic keys. An attacker with network access can exploit these timing differences without requiring authentication or user interaction. Successful exploitation could lead to high-impact compromises of confidentiality and integrity. The issue has been addressed in versions 1.80.2, 1.81.1, and 1.84.

Affected products

  • Bouncy Castle BC-JAVA (bcprov-jdk15to18) >= 1.71, < 1.80.2
  • Bouncy Castle BC-JAVA (bcprov-jdk14) >= 1.81, < 1.81.1
  • Bouncy Castle BC-JAVA (bcprov-jdk18on) >= 1.82, < 1.84

Identifiers

  • CVE-2026-5598
  • GHSA-p93r-85wp-75v3

Timeline

  • 2026-04-15: advisory: NVD publication date
  • 2026-04-17: disclosed: GitHub Advisory published
  • 2026-06-19: other: Advisory last updated

References

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