CVE-2026-65650 in Elgg
Summary
by MITRE • 07/22/2026
Elgg before 7.0.0 does not check image dimensions to prevent denial of service via a large avatar upload.
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Analysis
by VulDB Data Team • 07/22/2026
The vulnerability in Elgg versions prior to 7.0.0 represents a critical security flaw that enables denial of service attacks through improper validation of user avatar uploads. This weakness stems from the absence of dimensional checks on uploaded image files, allowing malicious actors to submit images with excessively large dimensions that can overwhelm system resources during processing. The vulnerability falls under the category of insufficient input validation as defined by CWE-20 and specifically relates to CWE-400 which addresses resource exhaustion issues in software applications. When users upload avatars without proper dimension verification, the system processes these files without bounds checking, creating an opportunity for attackers to consume excessive memory and processing power through carefully crafted image uploads.
The technical implementation of this vulnerability allows adversaries to exploit the image handling pipeline by uploading images with extremely high resolution dimensions that can cause memory allocation failures or process timeouts. This type of attack directly maps to the attacker tactics described in the MITRE ATT&CK framework under T1499 which covers resource exhaustion attacks, specifically targeting the availability aspect of the CIA triad. The flaw operates at the application layer where user-supplied data is processed without adequate validation of image properties such as width, height, or file size limits. System administrators typically expect standard avatar uploads to be within reasonable dimensions, but the lack of dimensional constraints allows for arbitrarily large images that can cause buffer overflows or memory exhaustion during image processing operations.
The operational impact of this vulnerability extends beyond simple denial of service conditions and can potentially lead to complete system unavailability or compromise of underlying infrastructure. When exploited, these large avatar uploads can cause application crashes, process termination, or resource starvation that affects not only the specific user account but potentially impacts other users within the same system context. The vulnerability represents a significant risk in multi-tenant environments where one malicious user could affect the availability of services for all users, making it particularly dangerous in enterprise and service provider deployments. Organizations relying on Elgg for community platforms, social networks, or collaborative spaces face increased risk of service disruption and potential data integrity issues when this vulnerability remains unaddressed.
Mitigation strategies should focus on implementing comprehensive image validation mechanisms that enforce dimensional limits during the upload process. System administrators should configure maximum width and height parameters for avatar uploads, typically restricting images to dimensions appropriate for display purposes such as 200x200 pixels or smaller. The recommended approach involves integrating image processing libraries that can automatically resize or reject oversized images before they are stored in the system. Additionally, implementing rate limiting and upload size restrictions provides layered defense against exploitation attempts. Organizations should also consider deploying automated monitoring systems to detect unusual upload patterns that might indicate attempted exploitation. The most effective remediation involves updating to Elgg 7.0.0 or later versions where dimensional validation has been properly implemented, as this addresses the root cause rather than relying on workarounds. Security teams should also implement regular vulnerability assessments and penetration testing to identify similar issues in other components of their web applications that might present analogous security weaknesses.