How severe is GHSA-g9mp-8g3h-3c5c?

No CVSS score has been assigned to GHSA-g9mp-8g3h-3c5c yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-g9mp-8g3h-3c5c?

GHSA-g9mp-8g3h-3c5c affects the following packages: github.com/flynn/noise (Go). Ecosystems affected: Go.

How do I fix GHSA-g9mp-8g3h-3c5c?

Update github.com/flynn/noise to 1.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g9mp-8g3h-3c5c is resolved across your whole dependency graph.

How do I detect GHSA-g9mp-8g3h-3c5c in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/flynn/noise, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate GHSA-g9mp-8g3h-3c5c if there is no patch (or I can't update yet)?

Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Is GHSA-g9mp-8g3h-3c5c actively exploited in the wild?

No public exploit code has been indexed for GHSA-g9mp-8g3h-3c5c yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for GHSA-g9mp-8g3h-3c5c?

GHSA-g9mp-8g3h-3c5c has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 28th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is GHSA-g9mp-8g3h-3c5c?

GHSA-g9mp-8g3h-3c5c is classified as CWE-311 (CWE-311). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was GHSA-g9mp-8g3h-3c5c published, and has it been updated?

GHSA-g9mp-8g3h-3c5c was published on February 15, 2022 and was last updated on November 8, 2023. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

flynn/noise has improper nonce handling yielding potential state DoSGHSA-g9mp-8g3h-3c5c

Fix: flynn/noise#44

GHSA-g9mp-8g3h-3c5c is a CWE-311 vulnerability in github.com/flynn/noise. A fix is available for github.com/flynn/noise — see the affected versions and patch details below.

Also known asCVE-2021-4239 GHSA-6cr6-fmvc-vw2pGO-2022-0425

Published

Feb 15, 2022

Updated

Nov 8, 2023

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 13, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for GHSA-g9mp-8g3h-3c5c.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk+0.01%

Lower risk than most CVEs28th percentile — riskier than 28% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

🐹github.com/flynn/noise

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

The Go package github.com/flynn/noise, a Noise Protocol implementation, has two bugs in nonce handling in versions prior to v1.0.0.

Issue 1: Potential nonce overflow

If 2<sup>64</sup> (~18.4 quintillion) or more messages are encrypted with Encrypt after handshaking, the nonce counter will wrap around, causing multiple messages to be encrypted with the same key and nonce, resulting in a potentially catastrophic weakening of the security properties of the symmetric cipher.

This has been resolved in the patched version by returning ErrMaxNonce from the CipherState Encrypt and Decrypt methods before the reserved maximum nonce is reached. If this error is encountered, the program should handshake again to start with a fresh CipherState.

Issue 2: Potential denial of service via invalid ciphertext

If an attacker sends an invalid ciphertext into one peer's Decrypt, the nonce is incremented unconditionally. This causes a desync of the CipherState due to a nonce mismatch between the peers, resulting in a failure to decrypt all subsequent messages. A new handshake will be required to establish a new CipherState.

This has been resolved in the patched version by returning authentication errors from Decrypt before incrementing the nonce.

Patches

Fixed in https://github.com/flynn/noise/pull/44, tagged as v1.0.0.

Acknowledgements

These issues were discovered during an audit of a user of this package (dnstt). Thanks to UC Berkley for commissioning the audit, and to David Fifield and Nathan Brown for their collaboration on the fixes. The fixed issues are noted in the audit as:

UCB-02-003 Potential nonce overflow in Noise protocol
UCB-02-006 DoS due to unconditional nonce increment

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/flynn/noise`	all versions	1.0.0`go get github.com/flynn/noise@v1.0.0`

Affected Products

1 product · 1 configurations

Application

noisenoiseprotocol

all

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/flynn/noise, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/flynn/noise to 1.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-g9mp-8g3h-3c5c is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.

Frequently Asked Questions

The Go package `github.com/flynn/noise`, a [Noise Protocol](https://noiseprotocol.org/) implementation, has two bugs in nonce handling in versions prior to v1.0.0. ### Issue 1: Potential nonce overflow If 2<sup>64</sup> (~18.4 quintillion) or more messages are encrypted with `Encrypt` after handshaking, the nonce counter will wrap around, causing multiple messages to be encrypted with the same key and nonce, resulting in a potentially catastrophic weakening of the security properties of the symmetric cipher. This has been resolved in the patched version by returning `ErrMaxNonce` from the `

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