Private-key recovery via nonconstant FrodoKEM decapsulation
Published Apr 15, 2026 · Updated Apr 15, 2026
Covert timing channel in vulnerable Bouncy Castle Java releases allows remote attackers to recover FrodoKEM private keys via decryption timing. FrodoEngine.sample() uses branching comparisons for noise sampling, while ctverify() branches on whether recomputed ciphertext arrays match. Exploitation requires repeated timing observations of FrodoKEM encapsulation decryption and affects 1.71 through 1.80.1, 1.81, and 1.82 through 1.83.
Summary
What happened
Covert timing channel in vulnerable Bouncy Castle Java releases allows remote attackers to recover FrodoKEM private keys via decryption timing. FrodoEngine.sample() uses branching comparisons for noise sampling, while ctverify() branches on whether recomputed ciphertext arrays match. Exploitation requires repeated timing observations of FrodoKEM encapsulation decryption and affects 1.71 through 1.80.1, 1.81, and 1.82 through 1.83.
The record
- CVE
- CVE-2026-5598
- Published
- Apr 15, 2026
- Updated
- Apr 15, 2026
- Vendor
- Legion of the Bouncy Castle Inc.
- Product
- Bouncy Castle Java
- Classifications
- CWE-385
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 15, 2026CVE publishedPublication date reported by the CVE source.
- Apr 15, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2.17.3 <1.84
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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