CVE-2026-93653 in Red Hat
Summary
by MITRE • 09/18/2026
A denial of service flaw was found in Poppler's Splash backend. A crafted PDF with tiling-pattern geometry approaching the int32 boundary can cause SplashOutputDev::tilingPatternFill to compute an attacker-controlled repeat count that drives an excessively long loop in the pattern-fill scanline routine, without a corresponding memory allocation. An attacker could exploit this by supplying a malicious PDF to an application that renders it via Poppler's Splash backend, causing the rendering process to consume 100% CPU for an attacker-controlled, extended duration.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified in Poppler’s Splash backend represents a critical denial of service flaw rooted in integer boundary handling and insufficient input validation within the PDF rendering engine. Specifically, the issue resides in the tiling-pattern geometry processing logic, where crafted PDF files containing patterns with dimensions or repeat counts approaching the maximum value for a signed 32-bit integer can trigger undefined behavior. When such a maliciously constructed document is processed by an application utilizing Poppler’s Splash backend, the function SplashOutputDev::tilingPatternFill calculates a repeat count based on attacker-controlled input without adequate bounds checking against system limits or memory availability. This miscalculation results in the pattern-fill scanline routine entering an excessively long loop that continues for an extended duration determined by the malicious payload rather than terminating as intended due to resource constraints or logical completion conditions.
From a technical perspective, this flaw is classified under CWE-190 Integer Overflow or Wraparound and CWE-787 Out-of-bounds Write if it were to lead to memory corruption, though in this specific instance, the primary impact is computational exhaustion rather than arbitrary code execution. The absence of a corresponding memory allocation for such massive repeat counts indicates that the vulnerability relies on CPU cycle consumption rather than heap or stack overflow mechanisms. This distinction is crucial for defenders as it means traditional buffer overflow protections may not mitigate this issue, and instead, resource monitoring and timeout mechanisms are required to detect and terminate the offending process. The lack of validation allows an attacker to force the rendering engine into a tight loop that consumes one hundred percent of available CPU resources on the affected system core or cores involved in the rendering task.
The operational impact of exploiting this vulnerability is severe for any service relying on Poppler for PDF processing, particularly those handling untrusted input such as email gateways, document management systems, web-based viewers, and automated content ingestion pipelines. An attacker who can supply a malicious PDF to these services can trigger a sustained denial of service condition that effectively renders the application or host system unusable due to resource starvation. This type of attack is particularly dangerous in multi-tenant environments where one user’s malicious input could degrade performance for all other users sharing the same infrastructure resources. The extended duration of the CPU spike means that even if the process eventually terminates, the latency introduced during the attack window can disrupt real-time services and cause cascading failures in dependent systems that expect timely responses from the PDF rendering component.
Mitigation strategies must focus on both immediate patching and architectural defenses. Users should immediately update Poppler to a version where this integer boundary check has been implemented within the Splash backend’s tiling pattern logic. In addition to software updates, organizations deploying services that process external PDFs should implement strict input validation at the ingestion layer to reject documents with suspiciously large geometric parameters before they reach the rendering engine. Furthermore, applying resource limits such as CPU quotas and execution timeouts via operating system-level controls or container orchestration policies can limit the blast radius of this vulnerability if exploited. Security teams should also monitor for anomalous spikes in CPU usage associated with PDF processing services to detect potential exploitation attempts in real time.
This incident aligns with ATT&CK technique T1496 Resource Hijacking, where attackers use compromised or vulnerable systems to consume significant resources, thereby denying service to legitimate users. The specific mechanism here involves abusing a logic flaw in the rendering pipeline rather than injecting malware for cryptomining or botnet activities, but the effect is identical: the unauthorized consumption of computational resources. Understanding this vector helps security architects design more resilient PDF processing pipelines that assume all external input may be malicious and enforce strict limits on geometric complexity and iteration counts within graphics libraries to prevent similar integer-based exhaustion attacks in future versions of rendering software.