Heap Over-Read in Libsoup via Unsigned Underflow
CVE-2026-66337 Published on July 24, 2026
Libsoup: libsoup: heap buffer over-read via integer underflow in soup_filter_input_stream_read_until()
A flaw was found in libsoup. An unsigned integer underflow in the soup_filter_input_stream_read_until() function causes a heap buffer over-read when parsing multipart HTTP responses. A malicious HTTP server can exploit this by sending a crafted multipart response, potentially causing the client application to crash or disclose sensitive heap memory.
Vulnerability Analysis
CVE-2026-66337 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a small impact on integrity, and a small impact on availability.
Timeline
Reported to Red Hat.
Made public.
Weakness Type
Out-of-bounds Read
The software reads data past the end, or before the beginning, of the intended buffer. Typically, this can allow attackers to read sensitive information from other memory locations or cause a crash. A crash can occur when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string. The expected sentinel might not be located in the out-of-bounds memory, causing excessive data to be read, leading to a segmentation fault or a buffer overflow. The software may modify an index or perform pointer arithmetic that references a memory location that is outside of the boundaries of the buffer. A subsequent read operation then produces undefined or unexpected results.
Products Associated with CVE-2026-66337
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