How severe is GHSA-c3m8-x3cg-qm2c?

GHSA-c3m8-x3cg-qm2c has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by GHSA-c3m8-x3cg-qm2c?

GHSA-c3m8-x3cg-qm2c affects the following packages: helmet-csp (npm). Ecosystems affected: npm.

How do I fix GHSA-c3m8-x3cg-qm2c?

Update helmet-csp to 2.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-c3m8-x3cg-qm2c is resolved across your whole dependency graph.

How do I detect GHSA-c3m8-x3cg-qm2c in my npm dependencies?

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

How do I mitigate GHSA-c3m8-x3cg-qm2c if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is GHSA-c3m8-x3cg-qm2c actively exploited in the wild?

No public exploit code has been indexed for GHSA-c3m8-x3cg-qm2c 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-c3m8-x3cg-qm2c published, and has it been updated?

GHSA-c3m8-x3cg-qm2c was published on September 3, 2020 and was last updated on September 29, 2021. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦

📦 npm

Not in CISA KEV

MEDIUM severity

Configuration Override in helmet-cspGHSA-c3m8-x3cg-qm2c

MEDIUMFix: helmetjs/csp@67a69ba

GHSA-c3m8-x3cg-qm2c is a medium-severity (CVSS 6.5) vulnerability in helmet-csp. A fix is available for helmet-csp — see the affected versions and patch details below.

Published

Sep 3, 2020

Updated

Sep 29, 2021

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 29, 2021 · OSV.dev, FIRST.org (EPSS)

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

54other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

helmet-cspnpm

659Kdownloads / week

Description

Versions of helmet-csp before to 2.9.1 are vulnerable to a Configuration Override affecting the application's Content Security Policy (CSP). The package's browser sniffing for Firefox deletes the default-src CSP policy, which is the fallback policy. This allows an attacker to remove an application's default CSP, possibly rendering the application vulnerable to Cross-Site Scripting.

Recommendation

Upgrade to version 2.9.1 or later. Setting the browserSniff configuration to false in vulnerable versions also mitigates the issue.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`helmet-csp`	≥ 1.2.2&&< 2.9.1	2.9.1`npm install helmet-csp@2.9.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for helmet-csp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update helmet-csp to 2.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-c3m8-x3cg-qm2c is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

Versions of `helmet-csp` before to 2.9.1 are vulnerable to a Configuration Override affecting the application's Content Security Policy (CSP). The package's browser sniffing for Firefox deletes the `default-src` CSP policy, which is the fallback policy. This allows an attacker to remove an application's default CSP, possibly rendering the application vulnerable to Cross-Site Scripting. ## Recommendation Upgrade to version 2.9.1 or later. Setting the `browserSniff` configuration to `false` in vulnerable versions also mitigates the issue.

O3 Security · Impact-Aware SCA

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