NATS server TLS missing ciphersuite settings when CLI flags used

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

not scored

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

(This advisory is canonically <https://advisories.nats.io/CVE/CVE-2021-32026.txt) Problem Description The NATS server by default uses a restricted set of modern ciphersuites for TLS. This selection can be overridden through configuration. The defaults include just RSA and ECDSA with either AES/GCM with a SHA2 digest or ChaCha20/Poly1305. The configuration system allows for extensive use of CLI options to override configuration settings. When using these to set a key/cert for TLS, the restricted ciphersuite settings were lost, enabling all ciphersuites supported by Go by default. None of these additional ciphersuites are broken, so the NATS maintainers have fixed this in public git and the next release is not being hurried, nor is this security advisory embargoed. Affected versions NATS Server: All versions prior to 2.2.3 fixed with nats-io/nats-server commit ffccc2e1bd (2021-04-29) Impact If a server administrator chooses to start the nats-server with TLS configuration parameters…

Published by the source

14 May 2024, 22:03 UTC

Last modified by the source

21 May 2024, 20:34 UTC

Source last checked

26 Oct 2026, 15:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-jj54-5q2m-q7pj

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# Patch Next advisory brief: CVE-2021-32026

Advisory: NATS server TLS missing ciphersuite settings when CLI flags used
IDs: CVE-2021-32026, GHSA-jj54-5q2m-q7pj
Record: https://patchnext.com/advisories/cve-2021-32026 (revision 1, source checked 26 Oct 2026, 15:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/nats-io/nats-server/v2 2.2.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/nats-io/nats-server/v2: affected < 2.2.3; fixed in 2.2.3

## Suggested inspection (read-only)
- Go github.com/nats-io/nats-server/v2: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/nats-io/nats-server/v2.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-jj54-5q2m-q7pj (GitHub-reviewed advisory GHSA-jj54-5q2m-q7pj lists affected ranges: Go github.com/nats-io/nats-server/v2 >=0 <2.2.3)

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