How severe is GHSA-f5v5-ccqc-6w36?

No CVSS score has been assigned to GHSA-f5v5-ccqc-6w36 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by GHSA-f5v5-ccqc-6w36?

GHSA-f5v5-ccqc-6w36 affects the following packages: async-nats (crates.io). Ecosystems affected: crates.io.

How do I fix GHSA-f5v5-ccqc-6w36?

Update async-nats to 0.29.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f5v5-ccqc-6w36 is resolved across your whole dependency graph.

How do I detect GHSA-f5v5-ccqc-6w36 in my crates.io dependencies?

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

How do I mitigate GHSA-f5v5-ccqc-6w36 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.

How does O3 Security protect against GHSA-f5v5-ccqc-6w36?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-f5v5-ccqc-6w36 can be triaged on real exposure rather than presence alone.

Is GHSA-f5v5-ccqc-6w36 actively exploited in the wild?

No public exploit code has been indexed for GHSA-f5v5-ccqc-6w36 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 GHSA-f5v5-ccqc-6w36 published, and has it been updated?

GHSA-f5v5-ccqc-6w36 was published on March 24, 2023 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.

🦀 crates.io

Not in CISA KEV

GHSA-f5v5-ccqc-6w36 — async-nats

Fix: nats-io/nats.rs@817a7b9

GHSA-f5v5-ccqc-6w36 is a security vulnerability in async-nats. A fix is available for async-nats — see the affected versions and patch details below.

async-nats vulnerable to TLS certificate common name validation bypass

Also known asRUSTSEC-2023-0027

Published

Mar 24, 2023

Updated

Nov 8, 2023

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 8, 2023 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

🦀async-nats

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

Description

The NATS official Rust clients are vulnerable to MitM when using TLS.

The common name of the server's TLS certificate is validated against the hostname provided by the server's plaintext INFO message during the initial connection setup phase. A MitM proxy can tamper with the host field's value by substituting it with the common name of a valid certificate it controls, fooling the client into accepting it.

Reproduction steps

The NATS Rust client tries to establish a new connection
The connection is intercepted by a MitM proxy
The proxy makes a separate connection to the NATS server
The NATS server replies with an INFO message
The proxy reads the INFO, alters the host JSON field and passes the tampered INFO back to the client
The proxy upgrades the client connection to TLS, presenting a certificate issued by a certificate authority present in the client's keychain. In the previous step the host was set to the common name of said certificate
rustls accepts the certificate, having verified that the common name matches the attacker-controlled value it was given
The client has been fooled by the MitM proxy into accepting the attacker-controlled certificate

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🦀crates.io	`async-nats`	all versions	0.29.0`cargo update -p async-nats --precise 0.29.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for async-nats, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update async-nats to 0.29.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-f5v5-ccqc-6w36 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-f5v5-ccqc-6w36 can be triaged on real exposure rather than presence alone.

Tailored to GHSA-f5v5-ccqc-6w36. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

The NATS official Rust clients are vulnerable to MitM when using TLS. The common name of the server's TLS certificate is validated against the `host`name provided by the server's plaintext `INFO` message during the initial connection setup phase. A MitM proxy can tamper with the `host` field's value by substituting it with the common name of a valid certificate it controls, fooling the client into accepting it. ## Reproduction steps 1. The NATS Rust client tries to establish a new connection 2. The connection is intercepted by a MitM proxy 3. The proxy makes a separate connection to the NAT

O3 Security · Impact-Aware SCA

Is GHSA-f5v5-ccqc-6w36 in your dependencies?

O3 Security finds GHSA-f5v5-ccqc-6w36 across crates.io dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

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