CVE-2015-5147 in Redcarpet
Summary
by MITRE
Stack-based buffer overflow in the header_anchor function in the HTML renderer in Redcarpet before 3.3.2 allows attackers to cause a denial of service (crash) and possibly execute arbitrary code via unspecified vectors.
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Analysis
by VulDB Data Team • 07/07/2017
The vulnerability identified as CVE-2015-5147 represents a critical stack-based buffer overflow within the HTML renderer component of the Redcarpet markdown processing library. This flaw exists specifically within the header_anchor function, which is responsible for generating anchor tags for markdown headers during the rendering process. The vulnerability affects Redcarpet versions prior to 3.3.2, making it a significant concern for applications that rely on this library for processing user-generated markdown content. The buffer overflow occurs when the library processes specially crafted markdown input that triggers the header_anchor function, leading to memory corruption that can result in unpredictable behavior.
The technical nature of this vulnerability stems from improper input validation and memory management within the header_anchor function. When processing markdown headers, the function fails to properly bounds-check input data before copying it to a fixed-size stack buffer. This allows attackers to overflow the buffer and overwrite adjacent memory locations, potentially corrupting the stack frame and execution flow. The vulnerability manifests as a crash during normal operation, but more concerning is the potential for arbitrary code execution when attackers can control the overflow data to redirect program execution. This type of vulnerability is classified as CWE-121 Stack-based Buffer Overflow, which is a well-documented weakness in software security where data is copied into a stack buffer without proper bounds checking.
The operational impact of CVE-2015-5147 extends beyond simple denial of service to include potential remote code execution capabilities, making it particularly dangerous in web applications. When exploited, this vulnerability can allow attackers to crash the application or potentially execute malicious code with the privileges of the affected process. This is especially problematic in web environments where markdown processing is used to render user-submitted content, as it creates an attack surface that can be exploited through simple input manipulation. The vulnerability can be leveraged in various attack scenarios including web application exploitation, server-side request forgery, and privilege escalation attacks, making it a serious concern for system administrators and security practitioners.
Mitigation strategies for CVE-2015-5147 focus primarily on upgrading to Redcarpet version 3.3.2 or later, which contains the necessary patches to address the buffer overflow issue. Organizations should conduct immediate vulnerability assessments to identify systems running affected versions of the library and prioritize patch deployment. Additionally, implementing input validation and sanitization measures can provide defense-in-depth protection, although these measures alone cannot fully prevent exploitation of the underlying vulnerability. Security monitoring should be enhanced to detect potential exploitation attempts, particularly those involving malformed markdown content that could trigger the vulnerable code path. The ATT&CK framework categorizes this type of vulnerability under T1190 Exploit Public-Facing Application, as it represents an exploitation of a software vulnerability in a publicly accessible component. Organizations should also consider implementing application whitelisting and sandboxing techniques to limit the potential impact should exploitation occur, while maintaining comprehensive logging and alerting mechanisms to detect anomalous behavior that might indicate attempted exploitation.