{"id":"CVE-2026-31842","aliases":["DEBIAN-CVE-2026-31842","EUVD-2026-19603","GHSA-mh87-c4c3-cgwf","UBUNTU-CVE-2026-31842"],"status":"published","title":"Tinyproxy HTTP request parsing desynchronization via case-sensitive Transfer-Encoding handling","description":"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 names are case-insensitive.","severity":{"version":"4.0","score":8.7,"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","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00585,"percentile":0.48435,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-444"],"published":"2026-04-07T11:17:33Z","modified":"2026-10-28T02:30:52Z","affected":[{"source":"osv","ecosystem":"Debian:12","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.11.1-2.1","1.11.1-2.1+deb12u1","1.11.1-3","1.11.1-4","1.11.2-1","1.11.2-1~bpo12+1","1.11.3-1","1.11.3-1~bpo13+1"]},{"source":"osv","ecosystem":"Debian:13","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.11.2-1","1.11.3-1","1.11.3-1~bpo13+1"]},{"source":"osv","ecosystem":"Debian:14","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.11.2-1","1.11.3-1","1.11.3-1~bpo13+1"]},{"source":"osv","ecosystem":"Ubuntu:Pro:14.04:LTS","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.8.3-3ubuntu1","1.8.3-3ubuntu14.04.1~esm1","1.8.3-3ubuntu14.04.1~esm2","1.8.3-3ubuntu14.04.1~esm3"]},{"source":"osv","ecosystem":"Ubuntu:Pro:16.04:LTS","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.8.3-3ubuntu1","1.8.3-3ubuntu16.04.1~esm1","1.8.3-3ubuntu16.04.1~esm2","1.8.3-3ubuntu16.04.1~esm3"]},{"source":"osv","ecosystem":"Ubuntu:Pro:18.04:LTS","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.8.4-2","1.8.4-3","1.8.4-5","1.8.4-5ubuntu0.1~esm1","1.8.4-5ubuntu0.1~esm2","1.8.4-5ubuntu0.1~esm3"]},{"source":"osv","ecosystem":"Ubuntu:20.04:LTS","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.10.0-2","1.10.0-4","1.10.0-4ubuntu0.1","1.10.0-4ubuntu0.2"]},{"source":"osv","ecosystem":"Ubuntu:Pro:22.04:LTS","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.10.0-5","1.11.0-1","1.11.0-1ubuntu0.1~esm1","1.11.0-1ubuntu0.1~esm2"]},{"source":"osv","ecosystem":"Ubuntu:24.04:LTS","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.11.1-2.1","1.11.1-3","1.11.1-3ubuntu0.1"]},{"source":"osv","ecosystem":"Ubuntu:25.10","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.11.2-1"]},{"source":"osv","ecosystem":"Ubuntu:26.10","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.11.3-1"]},{"source":"osv","ecosystem":"Ubuntu:26.04:LTS","package":"tinyproxy","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["1.11.2-1","1.11.2-1build1","1.11.3-1"]}],"products":[{"vendor":"tinyproxy project","product":"tinyproxy"},{"vendor":"tinyproxy_project","product":"tinyproxy"}],"references":[{"url":"https://github.com/tinyproxy/tinyproxy/issues/604","tags":["issue-tracking","technical-description","third-party-advisory","Exploit","Issue Tracking","report"]},{"url":"https://github.com/tinyproxy/tinyproxy","tags":["product","Product","package","report"]},{"url":"https://datatracker.ietf.org/doc/html/rfc7230","tags":["technical-description","Exploit","Technical Description","article","report"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-31842","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-mh87-c4c3-cgwf"},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/31xxx/CVE-2026-31842.json","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-31842","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2026-31842","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-31842","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2026-31842","title":"Tinyproxy HTTP request parsing desynchronization via case-sensitive Transfer-Encoding handling","description":"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 names are case-insensitive.","status":"published","published":"2026-04-07T11:17:33.621Z","modified":"2026-08-10T11:43:29.288Z","cvss":[{"version":"4.0","score":8.7,"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","level":"high","assessor":"cna"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"cna"},{"version":"2.0","score":7.8,"vector":"AV:N/AC:L/Au:N/C:N/I:N/A:C","assessor":"cna"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T14:19:50.92611Z"}],"euvd":[{"id":"EUVD-2026-19603","description":"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 names are case-insensitive.","status":"published","published":"2026-04-07T11:17:33Z","modified":"2026-08-10T11:43:29Z","cvss":[{"version":"4.0","score":8.7,"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","level":"high"}],"updated_at":"2026-11-02T18:02:06.086083Z"}],"ghsa":[{"id":"GHSA-mh87-c4c3-cgwf","title":"Tinyproxy through 1.11.3 is vulnerable to HTTP request parsing desynchronization due to a case...","description":"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 names are case-insensitive. By sending a request with Transfer-Encoding: Chunked, an unauthenticated remote attacker can cause Tinyproxy to misinterpret the request as having no body. In this state, Tinyproxy sets content_length.client to -1, skips pull_client_data_chunked(), forwards request headers upstream, and transitions into relay_connection() raw TCP forwarding while unread body data remains buffered. This leads to inconsistent request state between Tinyproxy and backend servers. RFC-compliant backends (e.g., Node.js, Nginx) will continue waiting for chunked body data, causing connections to hang indefinitely. This behavior enables application-level denial of service through backend worker exhaustion. Additionally, in deployments where Tinyproxy is used for request-body inspection, filtering, or security enforcement, the unread body may be forwarded without proper inspection, resulting in potential security control bypass.","status":"published","published":"2026-04-07T12:31:15Z","modified":"2026-04-07T12:31:21Z","cvss":[{"version":"4.0","score":8.7,"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:X","level":"high"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T15:07:11.075264Z"}],"nvd":[{"id":"CVE-2026-31842","description":"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 names are case-insensitive.","status":"published","published":"2026-04-07T12:16:21.04Z","modified":"2026-08-10T12:17:14.55Z","cvss":[{"version":"4.0","score":8.7,"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:X","level":"high","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"secondary"},{"version":"2.0","score":7.8,"vector":"AV:N/AC:L/Au:N/C:N/I:N/A:C","level":"high","assessor":"secondary"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T14:12:13.1424Z"}],"osv":[{"id":"CVE-2026-31842","title":"Tinyproxy HTTP request parsing desynchronization via case-sensitive Transfer-Encoding handling","description":"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 names are case-insensitive.","status":"published","published":"2026-04-07T11:17:33.621Z","modified":"2026-10-28T02:30:52.259014648Z","cvss":[{"version":"4.0","score":8.7,"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","level":"high"}],"cwes":["CWE-444"],"updated_at":"2026-11-02T15:45:01.218144Z"},{"id":"DEBIAN-CVE-2026-31842","description":"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 names are case-insensitive.","status":"published","published":"2026-04-07T12:16:21.04Z","modified":"2026-10-01T03:03:10.184803953Z","cvss":[{"version":"4.0","score":8.7,"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:X","level":"high"}],"updated_at":"2026-11-02T15:45:54.232518Z"},{"id":"UBUNTU-CVE-2026-31842","description":"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 names are case-insensitive.","status":"published","published":"2026-04-07T12:16:00Z","modified":"2026-10-17T12:58:08.638306475Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"},{"version":"4.0","score":8.7,"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","level":"high"}],"updated_at":"2026-11-02T16:56:16.036833Z"}]}}