CVE-2026-56860 in url
Summary
by MITRE • 08/14/2026
Previously, resolving relative paths containing parent directory ('..') segments performed string conversions and buffer rewrites on each step, resulting in quadratic time complexity and high memory allocation overhead. Now, path resolution operates on a byte buffer using index-based backtracking for '..' segments, eliminating the quadratic time complexity and significantly reducing memory allocations.
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Analysis
by VulDB Data Team • 08/14/2026
This vulnerability represents a critical performance and resource exhaustion issue in path resolution mechanisms that has significant implications for system security and stability. The flaw stems from an inefficient implementation approach where relative path traversal operations with parent directory references were processed through iterative string conversions and buffer rewrites, creating a computationally expensive operation that scales quadratically with input size. This design pattern fundamentally violates performance expectations and creates opportunities for resource exhaustion attacks. The original implementation suffered from quadratic time complexity O(n²) where n represents the length of the path, meaning that as path lengths increased exponentially, processing time grew at an even faster rate, leading to severe performance degradation and potential denial-of-service conditions.
The technical flaw manifests in how the system handles parent directory traversal segments denoted by '..' within relative paths. Traditional approaches would repeatedly convert string representations to buffers and rewrite memory locations during each step of '..', effectively creating a cascade of memory operations that multiplied with each additional parent directory reference. This approach not only consumed excessive CPU cycles but also generated substantial memory allocation overhead through repeated buffer reallocations and string manipulations. The vulnerability aligns with CWE-1321 which specifically addresses inefficient path resolution algorithms that can lead to resource exhaustion and performance degradation. From an attack perspective, this creates opportunities for attackers to craft maliciously long paths that can cause significant system slowdowns or complete service unavailability through resource exhaustion.
The operational impact of this vulnerability extends beyond simple performance degradation to encompass potential security implications including denial-of-service attacks that can affect critical system operations. Systems implementing vulnerable path resolution logic become susceptible to resource exhaustion attacks where an attacker can submit specially crafted paths containing numerous '..' segments to consume excessive CPU cycles and memory resources, potentially leading to system instability or complete service disruption. This vulnerability particularly affects applications that process user-supplied paths or work with file systems where path traversal operations are common, including web servers, file processing applications, and any system components that handle relative path resolution. The quadratic complexity means that even moderate-length malicious inputs can cause disproportionate resource consumption, making this vulnerability particularly dangerous in production environments where predictable performance is essential.
The remediation approach addresses these issues through a fundamental architectural change that implements index-based backtracking on byte buffers instead of string conversions and buffer rewrites. This optimization eliminates the quadratic time complexity by maintaining indices into the path buffer rather than performing repeated memory operations for each parent directory reference. The new implementation significantly reduces both CPU cycles required for path resolution and memory allocation overhead, creating a more efficient algorithm with linear time complexity O(n) where n is the path length. This change directly addresses the underlying performance characteristics that made systems vulnerable to resource exhaustion attacks while maintaining functional correctness of path resolution operations. The solution aligns with established best practices in secure coding and system design, as demonstrated by ATT&CK technique T1499 which covers resource exhaustion tactics that attackers use against system performance. Organizations implementing this fix should verify that the new implementation maintains compatibility with existing applications while providing robust protection against performance-based attacks that exploit inefficient path resolution algorithms.