{"id":"CVE-2026-55612","kind":"vulnerability","aliases":["CVE-2026-55612"],"related":[],"title":"uhttpd: invalid chunked POST lets attackers smuggle HTTP requests","description":"uhttpd is a small HTTP server. In unpatched repository snapshots, `client_poll_post_data()` in `client.c` consumes an invalid chunk-length line, such as a size exceeding INT_MAX, then clears `r->content_length` and `r->transfer_chunked` without draining the remaining body or setting `request.connection_close`. The completion check treats the chunked POST as finished and the keep-alive parser returns to `CLIENT_STATE_INIT`. Attacker-controlled body bytes aligned as a complete HTTP request are then parsed and processed as another request on the same connection, causing HTTP request smuggling and request-boundary desynchronization. Commits b78f518478794e16ba3568fc1258e40bf3e8eb3b and 34460b8211d676ef1b9f40d6b775c5e112933690 patch the issue.","summary":"uhttpd, a small HTTP server, mishandles an invalid chunk-length line in a chunked POST and stops reading the body early. An attacker can then get the leftover body bytes parsed as a separate request on the same keep-alive connection, which is HTTP request smuggling.","severity":"low","cvss":3.7,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["chunked-encoding","keep-alive","runtime","uhttpd"],"not_affected_if":["patched-commits"],"how_to_check":"- Check whether your uhttpd source includes commits `b78f518478794e16ba3568fc1258e40bf3e8eb3b` and `34460b8211d676ef1b9f40d6b775c5e112933690`.\n- Look at the uhttpd version or snapshot your build uses; the sources flag unpatched repository snapshots as affected.","fix":"- uhttpd: include commits `b78f518478794e16ba3568fc1258e40bf3e8eb3b` and `34460b8211d676ef1b9f40d6b775c5e112933690`, which the sources say patch the issue.","status":"open","published_at":"2026-10-30T22:16:54+00:00","first_seen_at":"2026-10-30T22:25:56+00:00","triaged_at":"2026-10-30T22:27:30+00:00","updated_at":"2026-10-30T22:27:30+00:00","category":"runtime","confidence":0.7,"triage":{"at":"2026-10-30T22:27:30Z","model":"claude-haiku-5-5","output":{"fix":"- uhttpd: include commits `b78f518478794e16ba3568fc1258e40bf3e8eb3b` and `34460b8211d676ef1b9f40d6b775c5e112933690`, which the sources say patch the issue.","reach":"network","title":"uhttpd: invalid chunked POST lets attackers smuggle HTTP requests","impact":"medium","summary":"uhttpd, a small HTTP server, mishandles an invalid chunk-length line in a chunked POST and stops reading the body early. An attacker can then get the leftover body bytes parsed as a separate request on the same keep-alive connection, which is HTTP request smuggling.","audience":"businesses","category":"runtime","nicknames":[],"who_cares":["uhttpd","keep-alive","chunked-encoding"],"confidence":0.7,"fix_status":"available","needs_auth":"no","worst_case":"Attacker smuggles requests past front-end checks on shared connections.","analyst_note":"","how_to_check":"- Check whether your uhttpd source includes commits `b78f518478794e16ba3568fc1258e40bf3e8eb3b` and `34460b8211d676ef1b9f40d6b775c5e112933690`.\n- Look at the uhttpd version or snapshot your build uses; the sources flag unpatched repository snapshots as affected.","plain_action":"","needs_analyst":false,"not_affected_if":["patched-commits"],"who_is_affected":"Systems running uhttpd built from unpatched repository snapshots that accept chunked POST requests over keep-alive connections are exposed. Builds that include the two patch commits, or that do not run uhttpd, can skip it. The sources do not say which deployments are most exposed.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"low"},"cost_usd":0.001319,"input_tokens":4284,"output_tokens":1781,"severity_before":"low"},"analyst_status":null,"analyst_note":null,"search":"'-2026':11A,14A '-55612':12A,15A '34460b8211d676ef1b9f40d6b775c5e112933690':175C 'align':145C 'aliv':21B,65B,133C 'anoth':157C 'attack':6A,47B,141C 'attacker-control':140C 'b78f518478794e16ba3568fc1258e40bf3e8eb3b':173C 'bodi':44B,53B,115C,143C 'boundari':170C 'byte':54B,144C 'caus':163C 'check':122C 'chunk':3A,17B,33B,38B,92C,110C,125C 'chunk-length':32B,91C 'chunked-encod':16B 'clear':103C 'client':82C,137C 'client.c':87C 'close':119C 'commit':172C 'complet':121C,148C 'connect':66B,162C 'consum':88C 'content':105C 'control':142C 'cve':10A,13A 'data':85C 'desynchron':171C 'drain':112C 'earli':45B 'encod':18B 'exceed':99C 'finish':128C 'get':50B 'http':8A,27B,69B,76C,149C,164C 'init':139C 'int':100C 'invalid':2A,31B,90C 'issu':178C 'keep':20B,64B,132C 'keep-al':19B,63B,131C 'leftov':52B 'length':34B,93C,106C 'let':5A 'line':35B,94C 'max':101C 'mishandl':29B 'pars':55B,153C 'parser':134C 'patch':176C 'poll':83C 'post':4A,39B,84C,126C 'process':155C 'r':104C,108C 'read':42B 'remain':114C 'repositori':80C 'request':9A,59B,70B,150C,158C,165C,169C 'request-boundari':168C 'request.connection':118C 'return':135C 'runtim':22B 'separ':58B 'server':28B,77C 'set':117C 'size':98C 'small':26B,75C 'smuggl':7A,71B,166C 'snapshot':81C 'state':138C 'stop':41B 'transfer':109C 'treat':123C 'uhttpd':1A,23B,24B,72C 'unpatch':79C 'without':111C","nicknames":[],"mitigations":[],"who_affected":"Systems running uhttpd built from unpatched repository snapshots that accept chunked POST requests over keep-alive connections are exposed. Builds that include the two patch commits, or that do not run uhttpd, can skip it. The sources do not say which deployments are most exposed.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"first_public_at":"2026-10-30T22:16:54+00:00","kev":null,"cvss_vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N","cvss_by":"security-advisories@github.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-55612","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55612","severity":null,"published_at":"2026-10-30T22:16:54+00:00","modified_at":"2026-10-30T22:16:54+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"}