CVE-2026-66752
Received Received - Intake

HTTP Request Smuggling in tiny-http Library

Publication date: 2026-07-28

Last updated on: 2026-07-28

Assigner: VulnCheck

Description
tiny-http through 0.12.0 contains an HTTP request smuggling vulnerability that allows remote attackers to desynchronize request framing by sending a Transfer-Encoding header with any value, including non-chunked codings, which causes the library to unconditionally apply chunk-decoding and discard Content-Length. Attackers can exploit the discrepancy between tiny_http's improper Transfer-Encoding parsing and a correctly-implemented front-end proxy to produce two distinct interpretations of a single byte stream, enabling request smuggling, and can additionally send non-chunked bodies with non-chunked Transfer-Encoding values to cause failed body reads that tie up connections and consume worker threads without signaling errors to clients.

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Meta Information

Published
2026-07-28
Last Modified
2026-07-28
Generated
2026-07-28
AI Q&A
2026-07-28
EPSS Evaluated
N/A
NVD
CVE-2026-66752
EUVD
EUVD-2026-49881

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
tiny-http tiny-http From 0.12.0 (inc)

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-444 The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.

Attack-Flow Graph

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Executive Summary

CVE-2026-66752 is an HTTP request smuggling vulnerability in the tiny-http library up to version 0.12.0. The issue occurs because tiny-http unconditionally applies chunk-decoding when any Transfer-Encoding header is present, regardless of its value. This violates RFC 9112 standards and creates inconsistent request framing between tiny-http and compliant front-end systems.

Detection Guidance

To detect this vulnerability, inspect HTTP requests for Transfer-Encoding headers with non-chunked values (e.g., 'identity') or conflicting Transfer-Encoding and Content-Length headers. Use tools like curl to send malformed requests and observe responses for inconsistencies or errors.

Impact Analysis

This vulnerability can allow attackers to smuggle malicious requests past front-end routing if tiny-http is behind a correctly parsing proxy. It can also cause denial-of-service by tying up server connections and consuming worker threads with malformed requests that receive no response.

Compliance Impact

This vulnerability primarily enables HTTP request smuggling, which could allow unauthorized data access or manipulation. For GDPR, this may lead to breaches of confidentiality or integrity of personal data. HIPAA compliance could be impacted if protected health information is exposed or altered due to request smuggling attacks.

Mitigation Strategies

Upgrade tiny-http to a patched version if available. Configure front-end proxies to reject requests with conflicting Transfer-Encoding and Content-Length headers. Implement strict Transfer-Encoding validation to enforce chunked encoding for requests with bodies.

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