CVE-2026-45352: medium-severity vulnerability in yhirose cpp-httplib
cpp-httplib DoS: Negative chunk-size in chunked Transfer-Encoding
Published · Updated
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13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 5.3epss 0.3%
cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.43.4, negative chunk-size in chunked Transfer-Encoding causes unbounded memory allocation and process crash. The ChunkedDecoder::read_payload function in cpp-httplib (httplib.h) parses the chunk-size field of HTTP chunked transfer encoding using std::strtoul(). Per the C standard (§7.22.1.4), strtoul silently accepts a leading minus sign, performing unsigned wrap-around: strtoul("-2", …, 16) returns ULONG_MAX − 1 (0xFFFFFFFFFFFFFFFE). The library's only guard (line 12833) rejects ULONG_MAX (the result of "-1"), but any other negative value such as "-2" passes validation. The resulting near-maximum value is stored in chunk_remaining and controls how many bytes the server's read loop consumes from the network. This vulnerability is fixed in 0.43.4.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Affected products
yhirose · cpp-httplibRelated CVEs — yhirose cpp-httplib
In the same product, most dangerous first.
CVE-2026-29076MEDIUMcpp-httplib: Stack Overflow Denial of Service (DoS) via std::regex in multipart filename parsingEPSS 0.7%CVE-2025-46728HIGHcpp-httplib has Unbounded Memory Allocation in Chunked/No-Length RequestsEPSS 0.7%CVE-2025-53629HIGHcpp-httplib Unbounded Memory Allocation in Chunked/No-Length Requests VulnerabilityEPSS 0.6%CVE-2025-53628MEDIUMcpp-httplib does not limit the length of a lineEPSS 0.5%CVE-2026-31870HIGHcpp-httplib Affected by Remote Process Crash via Malformed Content-Length Response HeaderEPSS 0.5%CVE-2025-52887HIGHcpp-httplib has unlimited number of http header fields, which causes memory leakEPSS 0.5%