CVE-2021-4239: The Noise protocol implementation suffers from weakened cryptographic security after encrypting 2^64 messages,

Routine

HIGH 7.5REMOTEMITIGATE

CVE-2021-4239 is a high-severity flaw (CVSS 7.5) affecting noise. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The Noise protocol implementation suffers from weakened cryptographic security after encrypting 2^64 messages, and a potential denial of service attack. After 2^64 (~18.4 quintillion) messages are encrypted with the Encrypt function, the nonce counter will wrap around, causing multiple messages to be encrypted with the same key and nonce. In a separate issue, the Decrypt function increments the nonce state even when it fails to decrypt a message.

Why this priority

High severity
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 68%)
CISA exploited list	No
Weakness	CWE-311
Published	2022-12-27
Last modified	2026-06-17

Publisher (CNA): Go Project · Vendor: noiseprotocol

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2022-12-27 22:15 UTCPublished CVE record published
2026-06-17 04:19 UTCUpdated Record last modified

noiseprotocol noise MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy noise || rpm -q noise || noise --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-4239?

noise: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-4239 being exploited?

CVE-2021-4239 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-4239 affect?

CVE-2021-4239 affects noise. Severity is high (CVSS 7.5). The Noise protocol implementation suffers from weakened cryptographic security after encrypting 2^64 messages, and a potential denial of service attack. After 2^64 (~18.4 quintillion) messages are encrypted with the Encrypt function, the no

How urgent is CVE-2021-4239?

Priority 39/100. High severity; Remotely exploitable, no login, no user action

References

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