{"id":"CVE-2026-112880","kind":"vulnerability","aliases":["CVE-2026-112880"],"related":[],"title":"hackney: unchecked proxy auth value lets CRLF split requests to proxy","description":"Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting') vulnerability in hackney_http_connect in benoitc hackney allows HTTP Request Splitting via the value a proxy_auth_fun callback returns. After a 407 response from an HTTP CONNECT proxy, hackney_http_connect:handle_proxy_auth/11 calls the caller's proxy_auth_fun with the status code and the response headers and writes the returned binary into the Proxy-Authorization line of the CONNECT retry without checking it. A CR, LF or NUL byte in that value adds header lines to the request sent to the proxy.\n\nThe value is attacker-influenced when the callback derives it from untrusted data, for example from the proxy's challenge headers. Other caller-supplied values on the CONNECT path, such as the target host and the request headers, were already checked for control bytes.\n\nThis issue affects hackney: from 2.0.0 before 4.9.0.","summary":"Erlang's hackney HTTP client writes whatever a proxy_auth_fun callback returns into a Proxy-Authorization header without stripping CR, LF or NUL bytes. If that value comes from untrusted data such as a proxy's challenge headers, an attacker can inject extra header lines into the CONNECT retry request sent to the proxy.","severity":"low","cvss":2.1,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["elixir","erlang","hackney","http-client","package"],"not_affected_if":["hackney-4.9.0-or-later","no-proxy","static-proxy-credentials"],"how_to_check":"- Run `rebar3 deps` or check `rebar.lock` for `hackney` at a version from `2.0.0` up to but not including `4.9.0`\n- Search your code for `proxy_auth_fun` and check whether its return value is built from data a remote party can influence","fix":"- Upgrade hackney to `4.9.0` or later\n- Until upgraded, make sure `proxy_auth_fun` returns only values built from trusted credentials and never from proxy response headers","status":"open","published_at":"2026-10-26T14:16:28+00:00","first_seen_at":"2026-10-26T14:30:36+00:00","triaged_at":"2026-10-26T14:32:53+00:00","updated_at":"2026-10-26T14:32:53+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-10-26T14:32:53Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade hackney to `4.9.0` or later\n- Until upgraded, make sure `proxy_auth_fun` returns only values built from trusted credentials and never from proxy response headers","reach":"network","title":"hackney: unchecked proxy auth value lets CRLF split requests to proxy","impact":"low","summary":"Erlang's hackney HTTP client writes whatever a proxy_auth_fun callback returns into a Proxy-Authorization header without stripping CR, LF or NUL bytes. If that value comes from untrusted data such as a proxy's challenge headers, an attacker can inject extra header lines into the CONNECT retry request sent to the proxy.","category":"package","nicknames":[],"who_cares":["erlang","elixir","hackney","http-client"],"confidence":0.7,"needs_auth":"unknown","worst_case":"Attacker injects extra headers into requests sent to the proxy","analyst_note":"","how_to_check":"- Run `rebar3 deps` or check `rebar.lock` for `hackney` at a version from `2.0.0` up to but not including `4.9.0`\n- Search your code for `proxy_auth_fun` and check whether its return value is built from data a remote party can influence","needs_analyst":false,"not_affected_if":["no-proxy","static-proxy-credentials","hackney-4.9.0-or-later"],"who_is_affected":"Only Erlang or Elixir applications that use hackney with HTTP CONNECT proxies and a proxy_auth_fun callback that derives its return value from untrusted input, such as the proxy's challenge headers. Applications that use hackney without proxies, or whose proxy_auth_fun returns fixed credentials, are not exposed.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"low"},"cost_usd":0.000669,"input_tokens":3555,"output_tokens":626,"severity_before":"low"},"analyst_status":null,"analyst_note":null,"search":"'-112880':14A,17A '-2026':13A,16A '2.0.0':231C '4.9.0':233C '407':115C 'add':170C 'affect':228C 'allow':100C 'alreadi':221C 'attack':66B,184C 'attacker-influenc':183C 'auth':4A,34B,109C,133C 'auth/11':127C 'author':42B,152C 'benoitc':98C 'binari':147C 'byte':50B,166C,225C 'call':128C 'callback':36B,111C,188C 'caller':130C,204C 'caller-suppli':203C 'challeng':63B,200C 'check':159C,222C 'client':23B,29B 'code':138C 'come':54B 'connect':74B,96C,120C,124C,156C,209C 'control':224C 'cr':46B,162C 'crlf':7A,84C 'cve':12A,15A 'data':57B,193C 'deriv':189C 'elixir':18B 'erlang':19B,25B 'exampl':195C 'extra':69B 'fun':35B,110C,134C 'hackney':1A,20B,27B,94C,99C,122C,229C 'handl':125C 'header':43B,64B,70B,88C,142C,171C,201C,219C 'host':215C 'http':22B,28B,87C,89C,95C,101C,119C,123C 'http-client':21B 'improp':81C 'influenc':185C 'inject':68B 'issu':227C 'let':6A 'lf':47B,163C 'line':71B,153C,172C 'neutral':82C 'nul':49B,165C 'packag':24B 'path':210C 'proxi':3A,11A,33B,41B,61B,80B,108C,121C,126C,132C,151C,179C,198C 'proxy-author':40B,150C 'request':9A,76B,102C,175C,218C 'request/response':90C 'respons':116C,141C 'retri':75B,157C 'return':37B,112C,146C 'sent':77B,176C 'sequenc':85C 'split':8A,91C,103C 'status':137C 'strip':45B 'suppli':205C 'target':214C 'uncheck':2A 'untrust':56B,192C 'valu':5A,53B,106C,169C,181C,206C 'via':104C 'vulner':92C 'whatev':31B 'without':44B,158C 'write':30B,144C","nicknames":[],"mitigations":[],"who_affected":"Only Erlang or Elixir applications that use hackney with HTTP CONNECT proxies and a proxy_auth_fun callback that derives its return value from untrusted input, such as the proxy's challenge headers. Applications that use hackney without proxies, or whose proxy_auth_fun returns fixed credentials, are not exposed.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-26T14:16:28+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:L/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":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-112880","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-112880","severity":null,"published_at":"2026-10-26T14:16:28+00:00","modified_at":"2026-10-26T14:16:28+00:00","first_seen_at":"2026-10-26T14:30:36+00:00","fetched_at":"2026-10-26T14:30:36+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"}