{"id":"CVE-2026-55614","kind":"vulnerability","aliases":["CVE-2026-55614"],"related":[],"title":"uhttpd: mixed-case Transfer-Encoding header enables HTTP request smuggling","description":"uhttpd is a small HTTP server. In unpatched repository snapshots, `client_parse_header()` in `client.c` lowercases header names but compares the `Transfer-Encoding` value to `chunked` using case-sensitive `strcmp`. A mixed-case transfer-coding token is accepted without enabling `r->transfer_chunked`, despite transfer-coding tokens being case-insensitive. On a keep-alive connection, the `chunked` POST body is left unread and request-shaped body bytes are parsed as another HTTP request, permitting HTTP request smuggling and boundary desynchronization. Commits ae015e099986ceace44975cb69629841a2d58d37 and 6641b050e5f7c7fd9ae92e8e119d6d6dfc6e9837 patch the issue.","summary":"uhttpd, a small HTTP server, compares the Transfer-Encoding header value to \"chunked\" case-sensitively, so a mixed-case value is accepted without chunked parsing being enabled. On keep-alive connections the unread chunked POST body is parsed as a second request, enabling request smuggling and desynchronization.","severity":"medium","cvss":6.9,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["embedded","http-server","openwrt","runtime","uhttpd"],"not_affected_if":["default-config","uhttpd-not-deployed"],"how_to_check":"- Check whether the running uhttpd build includes commit `ae015e099986ceace44975cb69629841a2d58d37` or `6641b050e5f7c7fd9ae92e8e119d6d6dfc6e9837`\n- Look for `client_parse_header()` in `client.c` and confirm the Transfer-Encoding comparison is case-insensitive\n- Identify whether uhttpd sits behind a proxy or handles keep-alive POST traffic directly","fix":"- Apply the patches in commits `ae015e099986ceace44975cb69629841a2d58d37` and `6641b050e5f7c7fd9ae92e8e119d6d6dfc6e9837`\n- Fixed release version: unknown","status":"open","published_at":"2026-10-30T22:16:55+00:00","first_seen_at":"2026-10-30T22:25:56+00:00","triaged_at":"2026-10-30T22:27:12+00:00","updated_at":"2026-10-30T22:27:12+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-10-30T22:27:12Z","model":"claude-haiku-5-5","output":{"fix":"- Apply the patches in commits `ae015e099986ceace44975cb69629841a2d58d37` and `6641b050e5f7c7fd9ae92e8e119d6d6dfc6e9837`\n- Fixed release version: unknown","reach":"network","title":"uhttpd: mixed-case Transfer-Encoding header enables HTTP request smuggling","impact":"medium","summary":"uhttpd, a small HTTP server, compares the Transfer-Encoding header value to \"chunked\" case-sensitively, so a mixed-case value is accepted without chunked parsing being enabled. On keep-alive connections the unread chunked POST body is parsed as a second request, enabling request smuggling and desynchronization.","audience":"businesses","category":"runtime","nicknames":[],"who_cares":["uhttpd","openwrt","embedded","http-server"],"confidence":0.6,"fix_status":"available","needs_auth":"unknown","worst_case":"Attacker smuggles requests past front-end controls and desynchronizes connections.","analyst_note":"Confirm affected release versions and fixed release from the NVD entry and upstream uhttpd repository; sources give only commit hashes.","how_to_check":"- Check whether the running uhttpd build includes commit `ae015e099986ceace44975cb69629841a2d58d37` or `6641b050e5f7c7fd9ae92e8e119d6d6dfc6e9837`\n- Look for `client_parse_header()` in `client.c` and confirm the Transfer-Encoding comparison is case-insensitive\n- Identify whether uhttpd sits behind a proxy or handles keep-alive POST traffic directly","plain_action":"","needs_analyst":true,"not_affected_if":["uhttpd-not-deployed","default-config"],"who_is_affected":"Exposure requires uhttpd to accept POST requests on keep-alive connections and to parse chunked bodies, typically on embedded or router-style deployments. Systems where uhttpd is not serving HTTP, or where a front-end proxy normalizes requests, are less exposed. The sources do not state which released versions are affected.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000812,"input_tokens":4269,"output_tokens":771,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-2026':14A,17A '-55614':15A,18A '6641b050e5f7c7fd9ae92e8e119d6d6dfc6e9837':168C 'accept':50B,118C 'ae015e099986ceace44975cb69629841a2d58d37':166C 'aliv':59B,137C 'anoth':155C 'bodi':65B,142C,150C 'boundari':163C 'byte':151C 'case':4A,41B,47B,106C,112C,131C 'case-insensit':130C 'case-sensit':40B,105C 'chunk':39B,52B,63B,103C,123C,140C 'client':87C 'client.c':91C 'code':115C,127C 'commit':165C 'compar':31B,96C 'connect':60B,138C 'cve':13A,16A 'despit':124C 'desynchron':76B,164C 'embed':19B 'enabl':9A,55B,72B,120C 'encod':7A,35B,100C 'header':8A,36B,89C,93C 'http':10A,21B,29B,81C,156C,159C 'http-server':20B 'insensit':132C 'issu':171C 'keep':58B,136C 'keep-al':57B,135C 'left':144C 'lowercas':92C 'mix':3A,46B,111C 'mixed-cas':2A,45B,110C 'name':94C 'openwrt':23B 'pars':53B,67B,88C,153C 'patch':169C 'permit':158C 'post':64B,141C 'r':121C 'repositori':85C 'request':11A,71B,73B,148C,157C,160C 'request-shap':147C 'runtim':24B 'second':70B 'sensit':42B,107C 'server':22B,30B,82C 'shape':149C 'small':28B,80C 'smuggl':12A,74B,161C 'snapshot':86C 'strcmp':108C 'token':116C,128C 'transfer':6A,34B,99C,114C,122C,126C 'transfer-cod':113C,125C 'transfer-encod':5A,33B,98C 'uhttpd':1A,25B,26B,77C 'unpatch':84C 'unread':62B,145C 'use':104C 'valu':37B,48B,101C 'without':51B,119C","nicknames":[],"mitigations":[],"who_affected":"Exposure requires uhttpd to accept POST requests on keep-alive connections and to parse chunked bodies, typically on embedded or router-style deployments. Systems where uhttpd is not serving HTTP, or where a front-end proxy normalizes requests, are less exposed. The sources do not state which released versions are affected.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"first_public_at":"2026-10-30T22:16:55+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/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","cvss_by":"security-advisories@github.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-55614","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55614","severity":null,"published_at":"2026-10-30T22:16:55+00:00","modified_at":"2026-10-30T22:16:55+00:00","first_seen_at":"2026-10-30T22:25:56+00:00","fetched_at":"2026-10-30T22:25:56+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}