CVE-2022-25875 in svelte
Summary
by MITRE • 07/12/2022
The package svelte before 3.49.0 are vulnerable to Cross-site Scripting (XSS) due to improper input sanitization and to improper escape of attributes when using objects during SSR (Server-Side Rendering). Exploiting this vulnerability is possible via objects with a custom toString() function.
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Analysis
by VulDB Data Team • 07/23/2022
The vulnerability identified as CVE-2022-25875 affects the svelte framework version prior to 3.49.0 and represents a critical cross-site scripting vulnerability that stems from inadequate input sanitization and improper attribute escaping during server-side rendering operations. This flaw specifically manifests when svelte processes objects that contain custom toString() functions during the server-side rendering phase, creating a pathway for malicious actors to inject arbitrary javascript code into web applications built with this framework.
The technical root cause of this vulnerability lies in svelte's handling of object serialization during server-side rendering where the framework fails to properly sanitize or escape object properties that contain custom toString() implementations. When svelte encounters an object with a custom toString() method during SSR, it does not adequately escape the output of this method before rendering it into the html document, allowing attackers to inject malicious javascript code through carefully crafted object structures. This issue maps directly to CWE-79 which describes improper neutralization of input during web page generation, and specifically aligns with CWE-116 which addresses improper encoding or escaping of output.
The operational impact of this vulnerability is severe as it enables remote code execution through cross-site scripting attacks, potentially allowing attackers to steal user sessions, deface websites, or redirect users to malicious content. Attackers can exploit this vulnerability by creating objects with malicious toString() functions that when processed during server-side rendering will be executed in the context of the victim's browser. This vulnerability affects all svelte applications that utilize server-side rendering and process user-provided data through object structures, making it particularly dangerous for applications that handle untrusted input.
The exploitation of this vulnerability requires minimal prerequisites as attackers only need to provide objects with custom toString() functions that contain malicious javascript payloads. The attack vector is particularly insidious because it leverages legitimate svelte functionality rather than requiring complex injection techniques, making detection and prevention more challenging. Security researchers have identified that this vulnerability falls under the ATT&CK technique T1566.001 which covers social engineering through spearphishing and T1203 which involves exploitation of remote services. Organizations using svelte frameworks should immediately upgrade to version 3.49.0 or later to mitigate this risk, as the fix involves implementing proper escaping mechanisms for object properties during server-side rendering operations.
Mitigation strategies should include immediate version upgrades to svelte 3.49.0 or higher, implementing comprehensive input validation and sanitization for all user-provided data, and establishing runtime monitoring to detect unusual object property behaviors. Additionally, organizations should conduct thorough security assessments of their svelte applications to identify any custom implementations that might be susceptible to similar issues, and consider implementing content security policies to limit the impact of potential successful attacks. The vulnerability highlights the importance of proper output escaping in server-side rendering environments and demonstrates how seemingly benign framework features can become security risks when not properly sanitized.