CVE-2025-26790 in Atlant
Summary
by MITRE • 09/14/2026
Withsecure Atlant with Capricorn engine before 2025-01-20_02 allows a Remote Denial of Service via an out-of-bounds memory read during processing of a document file by the antivirus engine.
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Analysis
by VulDB Data Team • 09/14/2026
The vulnerability identified in WithSecure Atlant, specifically within versions utilizing the Capricorn engine prior to the build dated 2025-01-20_02, represents a critical security flaw rooted in improper memory management during the analysis of document files. This issue manifests as an out-of-bounds read operation triggered when the antivirus scanning module processes specific types of documents. The Capricorn engine is designed to inspect file contents for malicious patterns and behaviors, but in this instance, the parsing logic fails to adequately validate input boundaries before accessing memory locations associated with the document structure. When a crafted or malformed document containing specially constructed data structures is submitted for analysis, the engine attempts to read from a memory address that lies outside the allocated buffer limits. This deviation from safe coding practices leads directly to an out-of-bounds memory read condition, which disrupts the normal execution flow of the scanning process and results in application instability.
From an operational perspective, this vulnerability primarily facilitates a Remote Denial of Service attack vector against systems running the affected version of WithSecure Atlant. Because the flaw is triggered during file processing, an attacker can exploit it by delivering a maliciously crafted document to a target system where the antivirus service is actively monitoring for new files or performing scheduled scans. Upon encountering this specific malformed input, the Capricorn engine encounters a fatal error due to the invalid memory access, causing the scanning process to crash. In many enterprise environments, such crashes can lead to the termination of the entire security agent service rather than just an isolated thread, thereby leaving the endpoint unprotected against other threats until the service is manually restarted or automatically recovered by system watchdogs. This creates a window of vulnerability where attackers could potentially execute further malicious activities without interference from the antivirus solution.
The technical classification of this flaw aligns with CWE-125, which describes Out-of-bounds Read vulnerabilities. These types of errors occur when software reads data past the end or before the beginning of the intended buffer, often leading to crashes, information disclosure, or unpredictable behavior depending on what memory contents are accessed and how the application handles the resulting exception state. In this specific context, while the immediate impact is denial of service due to a crash, out-of-bounds reads can sometimes be leveraged for more severe consequences such as sensitive data leakage if the read operation exposes adjacent memory structures containing credentials or internal system states. However, based on current reports, the primary exploitation path leads to service disruption rather than arbitrary code execution.
In terms of threat modeling and adversary tactics, this vulnerability maps closely to techniques found in the MITRE ATT&CK framework under Initial Access and Execution phases where availability is targeted. Specifically, it relates to resource exhaustion or denial-of-service attacks that aim to degrade the security posture of an organization by disabling protective controls. Attackers may use such exploits as part of a broader campaign to blind endpoint detection systems before deploying more destructive payloads like ransomware or data exfiltration tools. The ability to remotely trigger this condition via document delivery makes it particularly dangerous in environments where users frequently open attachments from external sources, including email clients and file sharing platforms integrated with the antivirus solution.
To mitigate this risk, organizations must prioritize immediate patching of WithSecure Atlant to a version released after 2025-01-20_02 or later, as indicated by the vendor's security advisory. Ensuring that endpoint protection agents are configured for automatic updates is crucial to maintaining defense against such vulnerabilities in real-time. Additionally, administrators should consider implementing network-level filtering or sandboxing solutions to analyze suspicious documents before they reach endpoints equipped with vulnerable antivirus software. Regular auditing of patch management processes and verification of agent versions across the enterprise infrastructure will help prevent exploitation windows from opening due to delayed updates. Monitoring logs for unexpected service restarts or crashes in the Capricorn engine can also serve as an early warning indicator that a potential exploit attempt is occurring, allowing security teams to respond proactively while patches are being deployed.