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Bouncy Castle FrodoKEM Private-Key Leakage via Timing Side Channel
CVE-2026-5598 is a timing side-channel vulnerability in Bouncy Castle BC-JAVA core's FrodoKEM decapsulation implementation. Non-constant-time comparisons in the FrodoEngine implementation can expose information through execution-time differences during decryption of encapsulations, potentially leaking private-key material. Affected BC-JAVA versions are 1.71 through versions before 1.80.2, 1.81 through versions before 1.81.1, and 1.82 through versions before 1.84.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation can disclose private-key material and undermine the confidentiality guarantees of affected FrodoKEM operations. The extent of key recovery and any resulting access to protected communications depend on the application's cryptographic usage and the attacker's ability to observe the timing channel. Code execution, privilege escalation, and denial of service are not established impacts of this vulnerability.
If you can’t patch tonight, do this now.
Until a corrected release can be deployed, avoid or disable affected FrodoKEM decapsulation functionality where feasible and limit access to systems exposing those cryptographic operations. Exposure restrictions are temporary risk-reduction measures and do not correct the non-constant-time comparisons.
Patch, then assume compromise.
Upgrade the affected Bouncy Castle provider to a corrected release for its package branch: bcprov-jdk15to18 1.80.2, bcprov-jdk14 1.81.1, or bcprov-jdk18on 1.84, or a subsequent release containing the fix. For bundled dependencies, install the applicable vendor security update rather than independently replacing libraries unless supported. Identified corrected product releases include Red Hat JBoss EAP 7.4.25 and 8.1.6, Java Buildpack 4.93.0, Ruby Buildpack 1.10.86, VMware Tanzu Data Flow on Kubernetes 2.0.6, and VMware Tanzu GemFire Management Console 1.4.5.
No validated public exploits yet. Hidden: 1 rejected by Mallory's analysis as not a working exploit.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
22 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.