Cryptographic nonce reuse and state desynchronization DoS
Published Dec 27, 2022 · Updated Apr 14, 2025
Improper nonce handling in Noise in Flynn Noise before 1.0.0 allows remote attackers to weaken encryption or interrupt service via crafted ciphertext. CipherState Encrypt can wrap its nonce after 2^64 messages, while CipherState Decrypt advances nonce state even when authentication fails, desynchronizing peers. No authentication is required for an attacker who can submit invalid ciphertext; the result is nonce reuse that weakens confidentiality or a subsequent-message encryption failure.
Summary
What happened
Improper nonce handling in Noise in Flynn Noise before 1.0.0 allows remote attackers to weaken encryption or interrupt service via crafted ciphertext. CipherState Encrypt can wrap its nonce after 2^64 messages, while CipherState Decrypt advances nonce state even when authentication fails, desynchronizing peers. No authentication is required for an attacker who can submit invalid ciphertext; the result is nonce reuse that weakens confidentiality or a subsequent-message encryption failure.
The record
- CVE
- CVE-2021-4239
- Published
- Dec 27, 2022
- Updated
- Apr 14, 2025
- Vendor
- Flynn
- Product
- Noise
- Classifications
- CWE-311, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Dec 27, 2022CVE publishedPublication date reported by the CVE source.
- Apr 14, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <1.0.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
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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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