CVE-2025-53629: cpp-httplib Unbounded Memory Allocation in Chunked/No-Length Requests Vulnerability

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2025-07-10 · updated 2026-06-17
Weakness: CWE-770

Description

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.23.0, incoming requests using Transfer-Encoding: chunked in the header can allocate memory arbitrarily in the server, potentially leading to its exhaustion. This vulnerability is fixed in 0.23.0. NOTE: This vulnerability is related to CVE-2025-53628.

Affected products

yhirose cpp-httplib: before 0.23.0 — fixed in 0.23.0

How to fix

Upgrade to a fixed version: yhirose cpp-httplib 0.23.0. Check the vendor advisory for mitigations.

References

https://github.com/yhirose/cpp-httplib/commit/17ba303889b8d4d719be3879a70639ab653efb99
https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-j6p8-779x-p5pw
https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-qjmq-h3cc-qv6w
https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-qjmq-h3cc-qv6w

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