How severe is CVE-2021-32026?

No CVSS score has been assigned to CVE-2021-32026 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2021-32026?

CVE-2021-32026 affects the following packages: github.com/nats-io/nats-server/v2 (Go). Ecosystems affected: Go.

How do I fix CVE-2021-32026?

Update github.com/nats-io/nats-server/v2 to 2.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32026 is resolved across your whole dependency graph.

How do I detect CVE-2021-32026 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/nats-io/nats-server/v2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-32026 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2021-32026 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-32026 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.

When was CVE-2021-32026 published, and has it been updated?

CVE-2021-32026 was published on May 14, 2024 and was last updated on September 10, 2026. 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

CVE-2021-32026 — nats-server

Fix: nats-io/nats-server@ffccc2e

CVE-2021-32026 is a security vulnerability in github.com/nats-io/nats-server/v2. A fix is available for github.com/nats-io/nats-server/v2 — see the affected versions and patch details below.

NATS server TLS missing ciphersuite settings when CLI flags used

Also known asGO-2024-2850

Published

May 14, 2024

Updated

Sep 10, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 10, 2026 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

🐹github.com/nats-io/nats-server/v2

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

(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 provided on the command-line, then clients can negotiate TLS ciphersuites which were not expected.

Workaround

Use a configuration file to set the TLS parameters instead of command-line options.

Solution

Upgrade the NATS server.

Credits

This issue was identified and reported by SimCorp.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/nats-io/nats-server/v2`	all versions	2.2.3`go get github.com/nats-io/nats-server/v2@v2.2.3`

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/nats-io/nats-server/v2, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/nats-io/nats-server/v2 to 2.2.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-32026 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

(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. Non

O3 Security · Impact-Aware SCA

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