CVE-2019-18855 in safe-svg
Summary
by MITRE
A Denial Of Service vulnerability exists in the safe-svg (aka Safe SVG) plugin through 1.9.4 for WordPress, related to potentially unwanted elements or attributes.
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Analysis
by VulDB Data Team • 02/11/2024
The CVE-2019-18855 vulnerability represents a critical denial of service weakness within the safe-svg WordPress plugin ecosystem, affecting versions up to 1.9.4. This vulnerability specifically targets the plugin's handling of svg file uploads and processing, creating a pathway for malicious actors to disrupt normal website operations through carefully crafted svg content. The issue stems from inadequate validation of svg elements and attributes during the sanitization process, allowing potentially harmful constructs to bypass security measures and potentially consume excessive system resources or trigger unexpected behavior within the WordPress environment.
The technical flaw manifests when the safe-svg plugin processes svg files that contain elements or attributes that should be restricted or removed during sanitization. This occurs because the plugin's validation logic fails to properly identify and neutralize potentially problematic svg constructs that could lead to resource exhaustion or unexpected execution paths. The vulnerability specifically relates to the plugin's inability to effectively filter out certain svg elements that may cause processing delays or resource consumption issues when parsed by the underlying system components. This weakness enables attackers to upload malicious svg files that, when processed by the plugin, can cause the target system to become unresponsive or consume excessive computational resources, ultimately leading to denial of service conditions.
The operational impact of this vulnerability extends beyond simple service disruption, as it can affect not only the targeted WordPress installation but also potentially impact the broader hosting environment. When exploited, the vulnerability allows attackers to consume disproportionate system resources through carefully crafted svg content, leading to server performance degradation or complete unavailability of the affected website. The vulnerability is particularly concerning in shared hosting environments where resource exhaustion on one site can impact neighboring websites hosted on the same infrastructure, creating cascading effects that amplify the attack's impact. Additionally, the vulnerability can be exploited without requiring elevated privileges or authentication, making it accessible to any user who can upload content to the WordPress site.
Mitigation strategies for CVE-2019-18855 should prioritize immediate plugin updates to version 1.9.5 or later, which contain the necessary fixes to properly sanitize svg content and prevent the exploitation of this denial of service vector. Organizations should implement additional defensive measures including restricting svg file uploads to trusted users only, implementing more robust content validation mechanisms, and monitoring for unusual resource consumption patterns that might indicate exploitation attempts. Network-level protections such as rate limiting and content filtering can provide additional layers of defense against exploitation attempts. The vulnerability aligns with CWE-400, which addresses unchecked resource consumption, and maps to ATT&CK technique T1499.004 for denial of service attacks, emphasizing the need for comprehensive security measures that address both the specific vulnerability and broader threat landscape considerations.