XSS with multiple Content Security Policy headers

XSS with multiple Content Security Policy headers

Announced

March 13, 2012

Reporter

Mike

Impact

Moderate

Products

Firefox, Firefox ESR, SeaMonkey, Thunderbird, Thunderbird ESR

Fixed in

• Firefox 11
• Firefox ESR 10.0.3
• SeaMonkey 2.8
• Thunderbird 11
• Thunderbird ESR 10.0.3

Description

Security Researcher Mike Brooks of Sitewatch reported that if multiple Content Security Policy (CSP) headers are present on a page, they have an additive effect page policy. Using carriage return line feed (CRLF) injection, a new CSP rule can be introduced which allows for cross-site scripting (XSS) on sites with a separate header injection vulnerability.

Firefox 3.6 and Thunderbird 3.1 are not affected by this vulnerability.

References

• Bad intersection of injected HTTP headers leads to Content Security Policy (CSP) Bypass
• CVE-2012-0451