Limited header injection when using dynamic overrides with user input in RubyGems secure_headers

Exploitation

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

CVSS

4.4 · CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2020-5216: 1.21% estimated exploitation activity in the next 30 days; percentile 68.43 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact If user-supplied input was passed into append/overridecontentsecuritypolicydirectives, a newline could be injected leading to limited header injection. Upon seeing a newline in the header, rails will silently create a new Content-Security-Policy header with the remaining value of the original string. It will continue to create new headers for each newline. e.g. would result in CSP supports multiple headers and all policies must be satisfied for execution to occur, but a malicious value that reports the current page is fairly trivial: Patches This has been fixed in 6.3.0, 5.2.0, and 3.9.0 Workarounds References https://github.com/twitter/secureheaders/security/advisories/GHSA-xq52-rv6w-397c The effect of multiple policies For more information If you have any questions or comments about this advisory: Open an issue in this repo DM us at @ndm on twitter

Published by the source

23 Jan 2020, 02:27 UTC

Last modified by the source

16 May 2023, 16:11 UTC

Source last checked

26 Oct 2026, 15:47 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-w978-rmpf-qmwg

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# Patch Next advisory brief: CVE-2020-5216

Advisory: Limited header injection when using dynamic overrides with user input in RubyGems secure_headers
IDs: CVE-2020-5216, GHSA-w978-rmpf-qmwg
Record: https://patchnext.com/advisories/cve-2020-5216 (revision 1, source checked 26 Oct 2026, 15:47 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: secure_headers 6.3.0, 5.2.0, 3.9.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- RubyGems secure_headers: affected >= 6.0.0, < 6.3.0; >= 5.0.0, < 5.2.0; < 3.9.0; fixed in 3.9.0, 6.3.0, 5.2.0

## Suggested inspection (read-only)
- RubyGems secure_headers: 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 secure_headers.
- 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-w978-rmpf-qmwg (GitHub-reviewed advisory GHSA-w978-rmpf-qmwg lists affected ranges: RubyGems secure_headers >=6.0.0 =5.0.0 =0 <3.9.0)

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