CVE-2026-116671 in Xpdf
Summary
by MITRE • 10/26/2026
Infinite loop in Xpdf 4.06 and earlier, due to incorrect validation of progression order field in JPEG 2000 image.
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Analysis
by VulDB Data Team • 10/26/2026
The vulnerability identified involves a critical logic error within the PDF rendering engine of Xpdf versions 4.06 and prior releases, specifically affecting the handling of JPEG 2000 images embedded within Portable Document Format files. This flaw stems from an insufficient validation mechanism applied to the progression order field found in the JPEG 2000 bitstream structure. In standard image processing workflows, particularly those involving lossless compression formats like JPEG 2000, the decoder must strictly adhere to defined parsing rules to ensure that data streams are interpreted correctly and terminated appropriately when expected. The specific defect lies in the failure of the parser to properly validate or bound-check the progression order parameters before initiating the decoding loop. This oversight allows an attacker to craft a malicious PDF containing a specially constructed JPEG 2000 image where the metadata indicates a sequence that does not terminate as anticipated by the decoder's internal state machine.
From a technical perspective, this misconfiguration leads directly to an infinite execution cycle within the application thread responsible for rendering the image data. When Xpdf processes such a malformed file, it enters a loop that continuously attempts to decode or process pixel data without encountering the necessary end-of-stream conditions or boundary checks required to break out of the iteration. This behavior is characteristic of CWE-835, which classifies loops that do not terminate correctly due to logic errors rather than resource exhaustion alone. The absence of proper bounds checking on the progression order field means the decoder continues to read from memory buffers indefinitely, consuming available CPU cycles and potentially leading to a denial of service condition for the user or system running the application.
The operational impact of this vulnerability is primarily centered around availability and stability. For end-users viewing documents locally, an infinite loop will cause the Xpdf viewer or any application integrating this library to become unresponsive, effectively freezing the interface until the process is manually terminated by the operating system. In server-side contexts where PDF processing occurs automatically for document conversion or archival purposes, such a flaw can lead to thread exhaustion and service degradation across multiple users sharing the same resources. This aligns with the ATT&CK technique T1496, Resource Hijacking, as the malicious input forces the target resource into an unproductive state that consumes computational power without delivering functional output. While this specific vector does not typically allow for remote code execution due to its nature as a logic loop rather than a memory corruption issue, it remains a significant risk in environments requiring high availability of document processing services.
Mitigation strategies must focus on both immediate patching and long-term defensive coding practices. The primary remediation is to upgrade Xpdf or the underlying Poppler library to version 4.07 or later, where this validation logic has been corrected to properly enforce termination conditions based on the JPEG 2000 specification. For organizations unable to immediately update their software stacks, implementing input sanitization at the network perimeter can help filter out suspicious PDF files containing malformed image headers before they reach the rendering engine. Additionally, developers integrating Xpdf into custom applications should consider wrapping document processing calls in timeout mechanisms or sandboxed environments with strict resource limits. This ensures that even if a malicious file triggers an infinite loop, the impact is contained and does not compromise the stability of the broader system infrastructure. Regular security audits focusing on third-party library integration points are also recommended to identify similar validation gaps in other media parsers.