What’s Vulnerable › Vulnerabilities

CVE-2026-28435: Payload size limit bypass via gzip decompression in ContentReader (streaming) allows oversized request bodies in cpp-httplib

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-03-04 · updated 2026-06-17
• Weakness: CWE-400

Description

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.35.0, cpp-httplib (httplib.h) does not enforce Server::set_payload_max_length() on the decompressed request body when using HandlerWithContentReader (streaming ContentReader) with Content-Encoding: gzip (or other supported encodings). A small compressed payload can expand beyond the configured payload limit and be processed by the application, enabling a payload size limit bypass and potential denial of service (CPU/memory exhaustion). This vulnerability is fixed in 0.35.0.

Affected products

• yhirose cpp-httplib: before 0.35.0 — fixed in 0.35.0

How to fix

Upgrade to a fixed version: yhirose cpp-httplib 0.35.0. Check the vendor advisory for mitigations.

References

• https://github.com/yhirose/cpp-httplib/commit/c99d7472b5cf4869d3897b9afc9792063a3d15a8
• https://github.com/yhirose/cpp-httplib/security/advisories/GHSA-xvfx-w463-6fpp

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