PT-2026-30811 · Tinyproxy+2 · Tinyproxy

Muxammadiyev Giyosiddin · Published 2026-04-07 · Updated 2026-05-01 · CVE-2026-31842

Positive Technologies (AI Summary)

CVSS v4.0

8.7

High

Base vector

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:X

Name of the Vulnerable Software and Affected Versions Tinyproxy versions 1.0 through 1.11.3

Description An issue exists in the way the Transfer-Encoding header is parsed in src/reqs.c. The is chunked transfer() function uses strcmp() to compare the header value against "chunked", failing to account for the fact that transfer-coding names are case-insensitive. An unauthenticated remote attacker can send a request with "Transfer-Encoding: Chunked", causing the software to misinterpret the request as having no body. Consequently, content length.client is set to -1, pull client data chunked() is skipped, and the system transitions into relay connection() raw TCP forwarding while body data remains buffered. This creates a desynchronization between the proxy and backend servers. RFC-compliant backends may wait indefinitely for chunked body data, leading to backend worker exhaustion and application-level denial of service. Furthermore, if the software is used for request-body inspection or security enforcement, the unread body may be forwarded without inspection, potentially bypassing security controls.

Recommendations At the moment, there is no information about a newer version that contains a fix for this vulnerability.

Exploit

DoS

HTTP Request/Response Smuggling

Weakness Enumeration

CWE-444

Related Identifiers

CVE-2026-31842

Affected Products

Tinyproxy

References · 11

• 🔥 https://github.com/tinyproxy/tinyproxy/issues/604 · Exploit
• 🔥 https://datatracker.ietf.org/doc/html/rfc7230 · Exploit
• https://osv.dev/vulnerability/DEBIAN-CVE-2026-31842 · Vendor Advisory
• https://security-tracker.debian.org/tracker/CVE-2026-31842 · Vendor Advisory
• https://osv.dev/vulnerability/UBUNTU-CVE-2026-31842 · Vendor Advisory
• https://ubuntu.com/security/CVE-2026-31842 · Vendor Advisory
• https://nvd.nist.gov/vuln/detail/CVE-2026-31842 · Security Note
• https://cve.org/CVERecord?id=CVE-2026-31842 · Security Note
• https://github.com/tinyproxy/tinyproxy · Note
• https://twitter.com/CVEnew/status/2045972457203609600 · Twitter Post
• https://twitter.com/DFIR_Lab/status/2050026733185769936 · Twitter Post