CVE-2026-56859 in encoding
Summary
by MITRE • 08/14/2026
Previously, DecodeElement would reset the depth counter causing it to never fire; this could lead to stack exhaustion.
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Analysis
by VulDB Data Team • 08/14/2026
The vulnerability described represents a critical flaw in XML parsing implementations that can lead to denial of service conditions through stack exhaustion. This issue manifests specifically within the DecodeElement function where a depth counter reset mechanism fails to properly terminate recursive parsing operations, creating an infinite loop scenario. The technical implementation error occurs when the depth counter is inadvertently reset during the decoding process, preventing proper stack depth monitoring and allowing recursive calls to continue indefinitely without termination.
This vulnerability directly impacts the stability and availability of applications that process XML data, particularly those susceptible to maliciously crafted input. When an attacker constructs XML content designed to trigger this specific parsing behavior, the application enters a state where it continuously processes nested elements without proper depth validation. The stack exhaustion occurs because each recursive call consumes additional stack space, and with the depth counter reset preventing proper termination, the system eventually exhausts available stack memory resources.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromise entire application availability and system stability. Applications utilizing affected XML parsing libraries become vulnerable to resource exhaustion attacks that can consume all available memory or CPU cycles, effectively rendering the service unavailable to legitimate users. This type of vulnerability is particularly dangerous in web applications and services that process untrusted XML input from external sources, as it provides a straightforward path for attackers to cause system instability.
From a cybersecurity perspective, this vulnerability aligns with CWE-770, which addresses allocation of resources without limits or with inadequate limits, and demonstrates characteristics consistent with attack patterns found in the MITRE ATT&CK framework under the resource exhaustion category. The flaw represents a classic example of inadequate input validation and state management within parsing routines, making it a prime candidate for exploitation in distributed denial of service scenarios.
Mitigation strategies should focus on implementing proper depth limiting mechanisms within XML parsers, ensuring that depth counters are correctly managed throughout the decoding process. Applications should enforce strict limits on nested element depth and implement timeout mechanisms to prevent indefinite processing of malformed input. Additionally, regular updates to XML parsing libraries and thorough input validation procedures can significantly reduce exposure to this type of vulnerability. Security teams should also consider implementing monitoring solutions that detect unusual resource consumption patterns indicative of stack exhaustion attacks, providing early warning capabilities for potential exploitation attempts.