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Published: 13 November 2018

There is a possible XSS vulnerability in Rack before 2.0.6 and 1.6.11. Carefully crafted requests can impact the data returned by the `scheme` method on `Rack::Request`. Applications that expect the scheme to be limited to 'http' or 'https' and do not escape the return value could be vulnerable to an XSS attack. Note that applications using the normal escaping mechanisms provided by Rails may not impacted, but applications that bypass the escaping mechanisms, or do not use them may be vulnerable.

From the Ubuntu Security Team

It was discovered that Rack incorrectly handled carefully crafted requests. A remote attacker could use this issue to execute a cross-site scripting (XSS) attack.



Cvss 3 Severity Score


Score breakdown


Package Release Status
Launchpad, Ubuntu, Debian
Released (1.6.4-4ubuntu0.1)
cosmic Ignored
(reached end-of-life)
disco Not vulnerable
eoan Not vulnerable
focal Not vulnerable
groovy Not vulnerable
hirsute Not vulnerable
impish Not vulnerable
jammy Not vulnerable
precise Does not exist

Released (1.5.2-1ubuntu0.1~esm1)
Released (1.5.2-3+deb8u2, 1.6.4-4+deb9u1, 1.6.11, 2.0.6)
Released (1.6.4-3ubuntu0.1)

Severity score breakdown

Parameter Value
Base score 6.1
Attack vector Network
Attack complexity Low
Privileges required None
User interaction Required
Scope Changed
Confidentiality Low
Integrity impact Low
Availability impact None
Vector CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N