CVE-2026-15714
Summary
by MITRE • 07/14/2026
An out-of-bounds read vulnerability was found in libsoup's multipart processing subsystem. The flaw exists in the soup_multipart_input_stream_read_headers() function inside soup-multipart-input-stream.c, which does not adequately restrict or validate the size of incoming multipart boundary strings. When processing a crafted HTTP response containing a malformed or oversized boundary parameter, the internal stream reader reads past the allocated buffer bounds. A remote, unauthenticated attacker can exploit this behavior to cause a service denial (DoS) through application failure or potentially read fragments of unauthorized memory metadata.
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Analysis
by VulDB Data Team • 07/14/2026
This vulnerability represents a critical out-of-bounds read flaw in the libsoup library's multipart processing functionality that poses significant security risks to web applications and services relying on this component. The issue is specifically located within the soup_multipart_input_stream_read_headers() function in the soup-multipart-input-stream.c source file, where insufficient input validation allows attackers to manipulate boundary string parameters during HTTP multipart data processing. The vulnerability stems from inadequate buffer size restrictions that fail to properly validate the length of incoming multipart boundary strings before processing them within the internal stream reader mechanism.
The technical exploitation of this flaw occurs when a remote, unauthenticated attacker crafts a malicious HTTP response containing an oversized or malformed boundary parameter that exceeds the allocated buffer boundaries. During normal operation, the multipart input stream reader attempts to parse and process these boundary strings, but due to the missing validation checks, it continues reading beyond the intended memory limits. This behavior creates a classic out-of-bounds memory access condition that can manifest in multiple ways depending on the system configuration and memory layout. The vulnerability specifically maps to CWE-129 Input Validation and Output Processing, where insufficient validation of input parameters leads to memory corruption issues.
The operational impact of this vulnerability extends beyond simple denial-of-service conditions, as it can potentially enable attackers to extract fragments of unauthorized memory content through the out-of-bounds read behavior. When applications process malicious multipart data containing oversized boundary strings, the stream reader may inadvertently access adjacent memory regions, potentially exposing sensitive information such as cryptographic keys, session tokens, or other confidential data stored in nearby memory locations. This characteristic transforms what might initially appear as a denial-of-service vulnerability into a more serious information disclosure threat that could compromise system security.
Service availability remains the primary concern for most exploitation scenarios, where attackers can reliably trigger application crashes or process failures through carefully crafted multipart boundary parameters. The DoS condition occurs when the out-of-bounds read causes memory corruption that leads to segmentation faults or application termination, effectively disrupting service availability for legitimate users. However, the potential for information disclosure adds complexity to risk assessment, particularly in environments where sensitive data might be accessible through memory fragments. This vulnerability impacts systems using libsoup version 2.54.0 and later versions, making it relevant across a wide range of applications including web servers, proxy services, and client applications that handle HTTP multipart content processing.
Mitigation strategies for this vulnerability should focus on both immediate patching and defensive programming approaches. The most effective solution involves applying the official security patches released by the libsoup maintainers that implement proper boundary string length validation and buffer size restrictions within the soup_multipart_input_stream_read_headers() function. Organizations should also consider implementing input validation controls at application layers that process multipart data, using techniques such as boundary parameter length limits and comprehensive content sanitization. Network-level protections can include HTTP filtering rules that identify and block suspicious multipart boundary patterns, while runtime monitoring solutions should be configured to detect abnormal memory access patterns that may indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation in security-critical components and aligns with ATT&CK technique T1203 Exploitation for Client Execution through memory corruption attacks targeting library functions.