CVE-2018-11507 in Free Lossless Image Format
Summary
by MITRE
An issue was discovered in Free Lossless Image Format (FLIF) 0.3. An attacker can trigger a long loop in image_load_pnm in image/image-pnm.cpp.
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Analysis
by VulDB Data Team • 03/17/2023
The vulnerability identified as CVE-2018-11507 resides within the Free Lossless Image Format (FLIF) 0.3 implementation, specifically targeting the image_load_pnm function located in the image/image-pnm.cpp source file. This issue represents a classic example of a resource exhaustion vulnerability that can be exploited through malformed input data. The FLIF format is designed for lossless image compression and is commonly used in scenarios where image quality must be preserved without any data loss. The affected component processes PNM (Portable AnyMap) format images, which are simple text-based image formats that serve as a common intermediate representation in image processing pipelines.
The technical flaw manifests as an infinite or extremely long loop within the image_load_pnm function, which occurs when processing specially crafted FLIF files that contain malformed PNM data. This condition arises from inadequate input validation and loop boundary checking within the image parsing logic. When an attacker provides a malicious FLIF file with corrupted PNM headers or malformed data structures, the parsing routine enters a state where it repeatedly processes the same data without proper termination conditions. The vulnerability stems from a lack of proper bounds checking and validation of image dimensions, pixel counts, or data segment lengths that would normally be validated during the image loading process.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can be leveraged to consume excessive system resources and potentially cause application crashes or system instability. In environments where FLIF files are processed automatically, such as in web applications, image processing pipelines, or content management systems, an attacker could exploit this vulnerability to exhaust CPU cycles, memory resources, or both. The sustained nature of the loop can lead to complete system resource exhaustion, making the affected service unavailable to legitimate users. This vulnerability is particularly concerning in server-side applications that handle user-uploaded images, as it provides a straightforward method for conducting resource exhaustion attacks without requiring sophisticated exploitation techniques.
Mitigation strategies for CVE-2018-11507 should focus on implementing robust input validation and introducing proper loop termination conditions within the image parsing logic. The most effective approach involves adding comprehensive bounds checking and maximum iteration limits to prevent infinite loops during image processing operations. Security practitioners should also consider implementing timeout mechanisms and resource usage monitoring to detect and prevent exploitation attempts. From a defensive perspective, this vulnerability aligns with CWE-835, which describes the weakness of infinite loops or other unbounded iterations that can lead to resource exhaustion. The ATT&CK framework categorizes this type of vulnerability under privilege escalation and denial of service tactics, as it can be used to compromise system availability and potentially create conditions for more sophisticated attacks. Organizations should prioritize updating to patched versions of FLIF libraries and implementing proper input sanitization measures to protect against similar vulnerabilities in other image processing components.