How severe is CVE-2020-5217?

CVE-2020-5217 has a CVSS score of 5.8/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2020-5217?

CVE-2020-5217 affects the following packages: secure_headers (RubyGems), secure_headers (RubyGems), secure_headers (RubyGems). Ecosystems affected: RubyGems.

How do I fix CVE-2020-5217?

Update secure_headers to 6.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5217 is resolved across your whole dependency graph.

How do I detect CVE-2020-5217 in my RubyGems dependencies?

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

How do I mitigate CVE-2020-5217 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-2020-5217 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2020-5217, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2020-5217?

CVE-2020-5217 has an EPSS (Exploit Prediction Scoring System) score of 1.8%, placing it in the 79th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2020-5217?

CVE-2020-5217 is classified as CWE-95 (CWE-95), CWE-74 (CWE-74). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-5217 published, and has it been updated?

CVE-2020-5217 was published on January 23, 2020 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

💎

💎 RubyGems

Not in CISA KEV

MEDIUM severity

CVE-2020-5217 — secure_headers

MEDIUMFix: twitter/secure_headers@936a160

CVE-2020-5217 is a medium-severity (CVSS 5.8) CWE-95 vulnerability in secure_headers. 1 public exploit reference exists, so weaponization risk is real. A fix is available for secure_headers — see the affected versions and patch details below.

Directive injection when using dynamic overrides with user input

Also known asGHSA-xq52-rv6w-397c

Published

Jan 23, 2020

Updated

Oct 20, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

1 known

Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

1.8%probability of exploitation in next 30 days

Lower Risk+0.02%

Lower risk than most CVEs79th percentile — riskier than 79% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2020-5217 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 394,803 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

3 pkgs affected

💎secure_headers💎secure_headers💎secure_headers

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

Description

Impact

If user-supplied input was passed into append/override_content_security_policy_directives, a semicolon could be injected leading to directive injection.

This could be used to e.g. override a script-src directive. Duplicate directives are ignored and the first one wins. The directives in secure_headers are sorted alphabetically so they pretty much all come before script-src. A previously undefined directive would receive a value even if SecureHeaders::OPT_OUT was supplied.

The fixed versions will silently convert the semicolons to spaces and emit a deprecation warning when this happens. This will result in innocuous browser console messages if being exploited/accidentally used. In future releases, we will raise application errors resulting in 500s.

Duplicate script-src directives detected. All but the first instance will be ignored.

See https://www.w3.org/TR/CSP3/#parse-serialized-policy

Note: In this case, the user agent SHOULD notify developers that a duplicate directive was ignored. A console warning might be appropriate, for example.

Patches

Depending on what major version you are using, the fixed versions are 6.2.0, 5.1.0, 3.8.0.

Workarounds

If you are passing user input into the above methods, you could filter out the input:

override_content_security_policy_directives(:frame_src, [user_input.gsub(";", " ")])

References

Reported in https://github.com/twitter/secure_headers/issues/418 https://www.w3.org/TR/CSP3/#parse-serialized-policy

For more information

If you have any questions or comments about this advisory:

Open an issue in this repo
DM @ndm on twitter

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
💎RubyGems	`secure_headers`	≥ 6.0.0&&< 6.2.0	6.2.0`bundle update secure_headers --conservative`
💎RubyGems	`secure_headers`	≥ 5.0.0&&< 5.1.0	5.1.0`bundle update secure_headers --conservative`
💎RubyGems	`secure_headers`	all versions	3.8.0`bundle update secure_headers --conservative`

Affected Products

1 product · 3 configurations

Application

secure headerstwitter

≥ 6.0.0 && < 6.2.0

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

In Secure Headers (RubyGem secure_headers), a directive injection vulner…

github.comNVDMay 2020

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for secure_headers, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update secure_headers to 6.2.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5217 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.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

Satellite 6 ships Secure Header rubygem, however it does not accept any user input in override_content_security_policy_directive or append_content_security_policy_directive. All directives are hard-coded and therefore, Satellite 6 is not vulnerable to this CVE. We may update this rubygem in future release.

Product	Fixed in	Advisory
Red Hat Satellite 6.8 for RHEL 7	`ansible-collection-redhat-satellite-0:1.3.0-1.el7sat`	RHSA-2020:4366

Frequently Asked Questions

### Impact If user-supplied input was passed into `append/override_content_security_policy_directives`, a semicolon could be injected leading to directive injection. This could be used to e.g. override a `script-src` directive. Duplicate directives are ignored and the first one wins. The directives in `secure_headers` are sorted alphabetically so they pretty much all come before `script-src`. A previously undefined directive would receive a value even if `SecureHeaders::OPT_OUT` was supplied. The fixed versions will silently convert the semicolons to spaces and emit a deprecation warning wh