CVE-2016-9964 in Bottle
Summary
by MITRE
redirect() in bottle.py in bottle 0.12.10 doesn't filter a "\r\n" sequence, which leads to a CRLF attack, as demonstrated by a redirect("233\r\nSet-Cookie: name=salt") call.
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Analysis
by VulDB Data Team • 10/12/2022
The vulnerability identified as CVE-2016-9964 affects the bottle.py web framework version 0.12.10 and represents a critical security flaw in the redirect() function implementation. This issue stems from inadequate input validation and sanitization within the framework's HTTP response handling mechanism. The vulnerability specifically exploits the absence of proper filtering for carriage return and line feed characters within the redirect functionality, creating an avenue for CRLF (Carriage Return Line Feed) injection attacks that can be leveraged by malicious actors to manipulate HTTP responses.
The technical flaw manifests when the redirect() function processes user-supplied input without properly sanitizing special character sequences including the newline character sequence. In the demonstrated attack scenario, a malicious payload such as redirect("233 Set-Cookie: name=salt") exploits this weakness by injecting additional HTTP headers into the response. The underlying mechanism allows attackers to inject arbitrary HTTP headers, including Set-Cookie directives, which can result in session hijacking, cross-site scripting, or other HTTP response manipulation attacks. This vulnerability directly maps to CWE-113, which describes improper neutralization of CRLF sequences in HTTP headers, and aligns with ATT&CK technique T1566.001 for initial access through spearphishing attachments.
The operational impact of this vulnerability extends beyond simple header injection, as it enables sophisticated attack vectors that can compromise user sessions and web application integrity. Attackers can leverage this flaw to inject malicious cookies, redirect users to phishing sites, or manipulate browser behavior through crafted HTTP responses. The vulnerability is particularly dangerous because it operates at the framework level, affecting all applications using vulnerable versions of bottle.py without requiring complex exploitation techniques. Organizations utilizing this framework face significant risk of unauthorized access and data compromise when this vulnerability remains unpatched.
Mitigation strategies for CVE-2016-9964 primarily involve immediate upgrading to a patched version of bottle.py where the redirect() function properly sanitizes input parameters and filters out CRLF sequences. Security teams should implement comprehensive input validation at multiple layers, including application-level sanitization and web application firewall rules that monitor for suspicious header injection patterns. Additionally, organizations should conduct thorough code reviews to identify other potential instances of similar vulnerabilities within their application frameworks, particularly focusing on HTTP response handling functions that process user-supplied data. The remediation process should include implementing proper output encoding mechanisms and establishing security testing procedures that specifically validate HTTP header generation to prevent future occurrences of CRLF injection vulnerabilities.