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CVE-2026-45352— cpp-httplib DoS: Negative chunk-size in chunked Transfer-Encoding

Quick assessment

Affected
yhirose cpp-httplib
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

cpp-httplib是yhirose个人开发者的一款使用C++语言编写的HTTP/HTTPS服务器和客户端库。 cpp-httplib 0.43.4之前版本存在安全漏洞，该漏洞源于分块传输编码中负分块大小导致无界内存分配和进程崩溃，ChunkedDecoder::read_payload函数解析分块大小时使用strtoul接受前导负号，导致接近最大值存储并控制读取循环消耗网络字节。

CVSS 5.3 · Medium EPSS 0.49% · P40

Affected Version Matrix 1

VendorProduct Version RangeStatus
yhirose cpp-httplib < 0.43.4 affected
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I. Basic Information for CVE-2026-45352

Vulnerability Information
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Vulnerability Title
cpp-httplib DoS: Negative chunk-size in chunked Transfer-Encoding
Source: CVE Program / CVE List V5
Vulnerability 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: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Source: CVE Program / CVE List V5
Vulnerability Type
输入验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
cpp-httplib 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
cpp-httplib是yhirose个人开发者的一款使用C++语言编写的HTTP/HTTPS服务器和客户端库。 cpp-httplib 0.43.4之前版本存在安全漏洞，该漏洞源于分块传输编码中负分块大小导致无界内存分配和进程崩溃，ChunkedDecoder::read_payload函数解析分块大小时使用strtoul接受前导负号，导致接近最大值存储并控制读取循环消耗网络字节。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
yhirose cpp-httplib < 0.43.4 -

II. Public POCs for CVE-2026-45352

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III. Intelligence Information for CVE-2026-45352

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Vendor Advisories for CVE-2026-45352 (1)

Same Patch Batch · yhirose · 2026-05-29 · 3 CVEs total

CVE-2026-45372 9.9 CRITICAL cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF
CVE-2026-46527 cpp-httplib: Malicious `X-Forwarded-For` Under Trusted-Proxy Configuration Triggers Empty

IV. Related Vulnerabilities

Same product: cpp-httplib
Same vendor: yhirose
Same weakness: CWE-20

V. Comments for CVE-2026-45352

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