CVE-2025-4969 in libsoup
Summary
by MITRE • 05/21/2025
A vulnerability was found in the libsoup package. This flaw stems from its failure to correctly verify the termination of multipart HTTP messages. This can allow a remote attacker to send a specially crafted multipart HTTP body, causing the libsoup-consuming server to read beyond its allocated memory boundaries (out-of-bounds read).
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Analysis
by VulDB Data Team • 06/22/2026
The vulnerability in the libsoup package represents a critical security flaw that affects numerous applications relying on this HTTP library for handling web communications. This issue stems from inadequate validation mechanisms within the multipart message processing functionality, specifically failing to properly verify the termination of multipart HTTP messages during parsing operations. The flaw exists at the core of how the library handles structured data transmission, where multipart content is commonly used for file uploads and complex data transfers in web applications.
The technical implementation of this vulnerability manifests as an out-of-bounds read condition that occurs when the libsoup library processes malformed multipart HTTP bodies. When a remote attacker crafts a specially designed payload containing improperly terminated multipart sections, the library's parsing routine attempts to access memory locations beyond its allocated buffer boundaries. This memory access violation can result in unpredictable behavior including application crashes, data corruption, or potentially more severe consequences depending on how the consuming applications handle such memory errors. The flaw operates at the protocol parsing layer, making it particularly dangerous as it can affect any server or application that utilizes libsoup for HTTP request processing.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable more sophisticated attacks. Applications consuming the affected libsoup library become susceptible to denial-of-service conditions where attackers can cause memory exhaustion through carefully crafted requests. Additionally, if the out-of-bounds read accesses sensitive memory regions containing authentication tokens, session data, or other confidential information, it could potentially lead to information disclosure vulnerabilities. The remote nature of this attack means that systems are vulnerable simply by processing HTTP requests, without requiring any special privileges or user interaction.
Organizations utilizing applications built on libsoup should implement immediate mitigations including updating to patched versions of the library where available, implementing input validation at application layers, and deploying network-based intrusion detection systems to monitor for suspicious multipart content patterns. The vulnerability aligns with CWE-129, which specifically addresses improper validation of length of input buffers, and can be mapped to ATT&CK technique T1059.007 for remote code execution through memory corruption vulnerabilities. Security teams should also consider implementing request size limits and content filtering mechanisms as additional defensive measures while awaiting official patches from the library maintainers.