CVE-2012-5486 in Plone
Summary
by MITRE
ZPublisher.HTTPRequest._scrubHeader in Zope 2 before 2.13.19, as used in Plone before 4.3 beta 1, allows remote attackers to inject arbitrary HTTP headers via a linefeed (LF) character.
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Analysis
by VulDB Data Team • 03/29/2022
The vulnerability described in CVE-2012-5486 represents a critical HTTP header injection flaw affecting Zope 2 versions prior to 2.13.19 and Plone versions before 4.3 beta 1. This vulnerability resides within the ZPublisher.HTTPRequest._scrubHeader function which is responsible for sanitizing HTTP headers in the Zope web application framework. The flaw specifically manifests when the application fails to properly validate and sanitize input containing linefeed characters, allowing malicious actors to inject arbitrary HTTP headers into responses. This type of vulnerability falls under the category of HTTP response splitting attacks as defined by CWE-113, which specifically addresses improper validation of HTTP headers. The vulnerability is particularly concerning because it enables attackers to manipulate HTTP responses in ways that can lead to various security breaches including cache poisoning, cross-site scripting attacks, and session hijacking.
The technical exploitation of this vulnerability occurs when an attacker submits malicious input containing linefeed characters such as \n or \r\n into parameters that are later processed by the _scrubHeader function. These linefeed characters are typically used to separate HTTP headers in the protocol specification, but when improperly handled, they can be used to inject additional headers into the HTTP response. The vulnerability stems from insufficient input validation and sanitization within the ZPublisher component of Zope, which is widely used in content management systems including Plone. This flaw represents a classic example of improper input validation as classified by CWE-20, where the application fails to properly validate or sanitize user-supplied data before incorporating it into HTTP responses. The injection can be leveraged to append headers such as Set-Cookie, Location, or other HTTP headers that can manipulate browser behavior or redirect traffic.
The operational impact of this vulnerability extends beyond simple header injection, as it can be used to craft sophisticated attacks against users of affected systems. When an attacker successfully injects HTTP headers, they can redirect users to malicious domains through Location headers, set malicious cookies through Set-Cookie headers, or manipulate caching behavior through Cache-Control headers. This can lead to various downstream security consequences including man-in-the-middle attacks, session fixation, and cross-site request forgery vulnerabilities. The attack vector is particularly dangerous because it can be exploited through any parameter that eventually gets processed by the vulnerable _scrubHeader function, making it difficult to fully mitigate without addressing the root cause. This vulnerability aligns with several techniques documented in the ATT&CK framework under the T1190 - Proxy Execution and T1566 - Phishing with Malicious Attachments categories, as attackers can use the header injection to redirect users to malicious sites or inject malicious content.
Organizations running affected versions of Zope or Plone systems face significant risk from this vulnerability, as it can be exploited by remote attackers without requiring authentication or special privileges. The remediation strategy involves upgrading to patched versions of Zope 2.13.19 or later and Plone 4.3 beta 1 or later, which contain proper input validation and sanitization routines. Additionally, administrators should implement input filtering at the application level and consider implementing web application firewalls to detect and block suspicious header injection attempts. The vulnerability demonstrates the critical importance of proper input validation in web applications and serves as a reminder of the potential consequences when sanitization routines fail to properly handle special characters in HTTP protocol elements. Organizations should also consider implementing comprehensive logging and monitoring of HTTP headers to detect potential exploitation attempts and maintain compliance with security standards such as those outlined in ISO 27001 and NIST SP 800-53 that emphasize the need for proper input validation and sanitization controls.