CVE-2026-71832 in Aria2
Summary
by MITRE • 08/24/2026
Aria2 version 1.37.0 and below is affected by a Divide By Zero issue in src/bittorrent_helper.cc, which allows a remote malicious user to cause a Denial of Service
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Analysis
by VulDB Data Team • 08/24/2026
The vulnerability identified in Aria2 versions 1.37.0 and earlier represents a critical arithmetic error located within the BitTorrent helper module, specifically in the source file bittorrent_helper.cc. This flaw manifests as a divide-by-zero condition, which occurs when the application attempts to perform division operations without adequately validating that the divisor is non-zero. In C++ applications, such an operation typically triggers a hardware exception or signal, leading to immediate process termination if not handled by robust error management routines. The presence of this vulnerability indicates a gap in input validation logic within the peer-to-peer protocol handling subsystem, where data derived from remote peers is processed without sufficient sanitization before being used as operands for arithmetic calculations.
From an operational perspective, this flaw allows any remote attacker who can interact with the Aria2 service to trigger a denial-of-service condition. By crafting specific BitTorrent metadata or torrent files that contain malformed parameters leading to zero-valued divisors during parsing or processing, an adversary can force the aria2c process to crash repeatedly. This disruption prevents legitimate users from downloading or uploading data through the affected instance of Aria2. Since Aria2 is often deployed as a background daemon for automated downloads and file management tasks, such instability can disrupt broader workflows that depend on consistent availability of the download manager service. The impact extends beyond simple application crashes; in environments where high availability is required, repeated exploitation could lead to resource exhaustion if crash recovery mechanisms are not configured or fail to restart the process efficiently.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-369, which describes an error condition that occurs when a division by zero takes place. It also relates closely to CWE-20, Improper Input Validation, as the root cause is the failure to verify the integrity and validity of external data before its use in critical operations. In terms of offensive security frameworks, this exploit scenario maps to MITRE ATT&CK technique T1499, Endpoint Denial of Service, specifically under sub-techniques involving application exhaustion or resource consumption via software flaws. The attack vector is classified as remote and network-accessible, requiring no authentication if the Aria2 service is exposed on a public interface or accessible within an untrusted network segment.
Mitigation strategies for this vulnerability primarily involve upgrading to a patched version of Aria2 where the divide-by-zero logic has been corrected with proper checks ensuring divisors are non-zero before execution. For organizations unable to immediately patch, deploying web application firewalls or intrusion prevention systems that can detect and block malformed BitTorrent metadata packets may provide temporary relief. Additionally, configuring system-level resource limits such as ulimits in Linux environments can help contain the impact of crashes by limiting core dump sizes and ensuring automatic restarts via service managers like systemd are properly configured to maintain availability despite repeated failures. Regular auditing of third-party dependencies and keeping all software components updated is essential to prevent exploitation of known arithmetic vulnerabilities in network-facing services.