CVE-2026-45352

5.3 MEDIUM

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library

Published: 2026-05-29 · Last updated: 2026-06-02

Severity and scoring

CVSS: 5.3 MEDIUM
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CWE: CWE-1285, CWE-20, CWE-770

Affected products

Vendor	Product
yhirose	cpp-httplib

Description

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.

Source: NVD

References

[NVD]https://nvd.nist.gov/vuln/detail/CVE-2026-45352
[Vendor advisory]https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-h6wq-j5mv-f3q8
[Vendor advisory]https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-h6wq-j5mv-f3q8

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