CVE-2026-31842
Tinyproxy Project Tinyproxy ≤ 1.11.3
Raw vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-31842 is a high-severity HTTP Request/Response Smuggling (CWE-444) vulnerability in Tinyproxy Project Tinyproxy. Its CVSS base score is 8.7 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked at the 46th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified map to SC-7 (Boundary Protection) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-31842 is a vulnerability in Tinyproxy through version 1.11.3 that enables HTTP request parsing desynchronization due to a case-sensitive comparison of the Transfer-Encoding header in src/reqs.c. The is_chunked_transfer() function employs strcmp() to match the header value against "chunked", disregarding RFC 7230's requirement for case-insensitive transfer-coding names. This flaw carries a CVSS v3.1 base score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H) and maps to CWE-444 (Inconsistent Interpretation of HTTP Requests).
An unauthenticated remote attacker can exploit this by crafting a request with "Transfer-Encoding: Chunked", prompting Tinyproxy to treat it as having no body. It then sets content_length.client to -1, bypasses pull_client_data_chunked(), forwards only the request headers upstream, and shifts to relay_connection() for raw TCP forwarding, leaving unread body data buffered. This desynchronizes Tinyproxy from RFC-compliant backends like Node.js or Nginx, which await the chunked body and hang indefinitely, enabling application-level denial-of-service through backend worker exhaustion. In configurations relying on Tinyproxy for request-body inspection, filtering, or security enforcement, the unprocessed body may bypass these controls.
The vulnerability is documented in the Tinyproxy GitHub repository at https://github.com/tinyproxy/tinyproxy and specifically tracked in issue #604 at https://github.com/tinyproxy/tinyproxy/issues/604. RFC 7230, available at https://datatracker.ietf.org/doc/html/rfc7230, outlines the case-insensitive header handling standard. Security practitioners should monitor the Tinyproxy repository for patches addressing versions through 1.11.3.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-19603
Vulnerability Data
Tinyproxy through 1.11.3 is vulnerable to HTTP request parsing desynchronization due to a case-sensitive comparison of the Transfer-Encoding header in src/reqs.c. The is_chunked_transfer function uses strcmp to compare the header value against "chunked", even though RFC 7230 specifies that transfer-coding…
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names are case-insensitive.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V4.1.3V4.2.4V1.5.3V4.1.1
Mitigating Controls (NIST 800-53 r5) AI
Boundary protection at external interfaces can enforce consistent HTTP request/response parsing rules between intermediaries and endpoints.
Validating HTTP inputs at the intermediary prevents malformed messages from being interpreted inconsistently downstream.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Network monitoring can detect smuggling attempts via anomalous HTTP traffic or logs, while eliminating the inconsistency directly aids detection of such events.
Network protections can enforce consistent HTTP proxy/firewall behavior to block smuggling, and removing the weakness helps prevent unauthorized access via request smuggling.
Configuration management can enforce uniform HTTP parsing rules across intermediaries, directly mitigating inconsistent interpretation.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Network security controls can enforce consistent HTTP parsing and proxy behavior that mitigates request smuggling.
Secure network services include hardening proxies and gateways against inconsistent HTTP interpretation.
Secure SDLC practices require threat modeling and testing for HTTP parsing inconsistencies in intermediaries.
Application security requirements can mandate strict HTTP message validation and canonicalization.
Secure architecture principles include consistent protocol handling and defense-in-depth for proxies.
Secure coding standards can require strict HTTP header and request validation to prevent smuggling.