CVE-2011-2691 in libpng
Summary
by MITRE
The png_err function in pngerror.c in libpng 1.0.x before 1.0.55, 1.2.x before 1.2.45, 1.4.x before 1.4.8, and 1.5.x before 1.5.4 makes a function call using a NULL pointer argument instead of an empty-string argument, which allows remote attackers to cause a denial of service (application crash) via a crafted PNG image.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 11/14/2021
The vulnerability identified as CVE-2011-2691 represents a critical flaw in the libpng library that affects multiple version streams including 1.0.x, 1.2.x, 1.4.x, and 1.5.x releases prior to specific patch versions. This issue stems from improper error handling within the png_err function located in the pngerror.c source file, where the implementation fails to properly validate pointer arguments during error processing. The flaw manifests when the library encounters malformed PNG image data that triggers the error handling routine, causing the application to attempt a function call with a NULL pointer instead of an appropriate empty string argument. This fundamental programming error creates a condition where legitimate error processing becomes a vector for system instability.
The technical nature of this vulnerability aligns with CWE-476 which specifically addresses NULL pointer dereference conditions in software implementations. The flaw operates through a classic buffer overflow scenario where the application's error handling mechanism itself becomes the attack surface. When remote attackers craft malicious PNG files designed to trigger specific error conditions, the libpng library's error processing routine executes with a NULL pointer argument, leading to immediate application termination or crash. This behavior represents a denial of service condition that can be exploited across any application relying on libpng for image processing functionality, including web servers, image viewers, and content management systems.
The operational impact of CVE-2011-2691 extends beyond simple service disruption to encompass broader security implications for systems processing untrusted image data. Applications utilizing vulnerable versions of libpng become susceptible to remote exploitation without requiring authentication or specialized privileges from attackers. The vulnerability can be leveraged to cause persistent service degradation across multiple platforms and applications, as any software component that processes PNG images through the affected library versions becomes a potential target. This makes the flaw particularly dangerous in server environments where image processing is common and automated, potentially enabling attackers to create sustained denial of service conditions that can impact availability and user experience.
Mitigation strategies for this vulnerability center on immediate version updates to patched releases of libpng, specifically upgrading to versions 1.0.55, 1.2.45, 1.4.8, and 1.5.4 or later. System administrators should conduct comprehensive inventory assessments to identify all applications and services utilizing vulnerable libpng versions, as the library is widely deployed across various software ecosystems. Additional protective measures include implementing input validation controls at application boundaries, deploying network-based intrusion detection systems to monitor for exploitation attempts, and establishing robust application sandboxing to limit potential damage from successful attacks. The remediation approach should also incorporate regular security assessments and patch management procedures to prevent similar vulnerabilities from emerging in other components of the software supply chain. Organizations should consider implementing automated vulnerability scanning tools that can detect the presence of vulnerable library versions and ensure timely deployment of security patches across their infrastructure.