An integer underflow in the soup_filter_input_stream_read_until() function of libsoup triggers a heap buffer over-read when parsing multipart HTTP responses. The flaw allows a hostile HTTP server to send a specially crafted multipart payload that causes the client application to read beyond the intended buffer boundary, potentially exposing sensitive heap contents and causing the process to crash. This is a classic case of CWE‑125 (Out‑of‑Bounds Read).

Red Hat Enterprise Linux 6, 7, 8, 9, and 10 ship the vulnerable libsoup library and are therefore susceptible. All systems running these RHEL variants with the default libraries may be exposed until an update is applied.

The CVSS score of 6.5 reflects moderate severity, while the EPSS score of less than 1% indicates a low likelihood of current exploitation. The vulnerability is not listed in the CISA KEV catalog. Attackers would need to position a malicious HTTP server that delivers multipart responses to a victim using libsoup. Because the flaw originates from network traffic, it is considered a remote threat that can trigger denial‑of‑service or partial disclosure of memory. The low exploitation probability and moderate CVSS mean that the potential impact warrants timely patching, particularly for systems that routinely consume multipart HTTP responses from untrusted sources.