{"id":"EEF-CVE-2026-74836","summary":"HTTP/2 connection-window starvation pins Plug processes indefinitely in Bandit","details":"## Summary\n\nAllocation of Resources Without Limits or Throttling vulnerability in mtrudel bandit allows an unauthenticated remote attacker to pin an unbounded number of HTTP/2 stream processes indefinitely via connection-level flow control. When a stream's response body outruns the HTTP/2 connection-level send window (default 65,535 bytes, shared across all streams on the connection), `Bandit.HTTP2.Connection` queues the remaining bytes and a reply closure in `pending_sends` and the stream process blocks forever inside a synchronous call to the connection process. Nothing bounds that wait and nothing purges the queue: a client `RST_STREAM` for the blocked stream is delivered to its mailbox but never read while it is stuck inside the call, so cancelling frees nothing, and periodic PING frames keep the transport-level read timeout from ever firing. The equivalent block on the stream-level send window is already bounded at 15 seconds; the connection-level path had no such bound.\n\nEach stalled stream pins its process, Plug state, and any resource the Plug holds across the blocked write, such as a pooled upstream connection in a reverse-proxy Plug. The attacker chooses any endpoint whose response exceeds the connection window (common for most non-trivial payloads), grants a generous stream-level window so only the connection window limits it, and keeps the connection alive with periodic PINGs; the primitive is repeatable across streams and connections at the cost of one idle socket each.\n\nThis issue affects bandit: from 0.3.4 before 1.12.5.","aliases":["CVE-2026-74836","GHSA-xj8g-532w-jv94"],"modified":"2026-09-09T00:30:03.556324029Z","published":"2026-08-20T21:11:18.999Z","database_specific":{"capec_ids":["CAPEC-130"],"cpe_ids":["cpe:2.3:a:mtrudel:bandit:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-770"]},"references":[{"type":"ADVISORY","url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-xj8g-532w-jv94"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-74836.html"},{"type":"FIX","url":"https://github.com/mtrudel/bandit/commit/f6914aad14bb1365dd6f306aa592cfb0819bed3e"},{"type":"PACKAGE","url":"https://hex.pm/packages/bandit"}],"affected":[{"package":{"name":"bandit","ecosystem":"Hex","purl":"pkg:hex/bandit"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.3.4"},{"fixed":"1.12.5"}]}],"versions":["0.3.4","0.3.5","0.3.6","0.3.7","0.3.8","0.3.9","0.4.0","0.4.1","0.4.10","0.4.2","0.4.3","0.4.4","0.4.5","0.4.6","0.4.7","0.4.8","0.4.9","0.5.0","0.5.1","0.5.10","0.5.11","0.5.2","0.5.3","0.5.4","0.5.5","0.5.6","0.5.7","0.5.8","0.5.9","0.6.0","0.6.1","0.6.10","0.6.11","0.6.2","0.6.3","0.6.4","0.6.5","0.6.6","0.6.7","0.6.8","0.6.9","0.7.0","0.7.1","0.7.2","0.7.3","0.7.4","0.7.5","0.7.6","0.7.7","1.0.0","1.0.0-pre.1","1.0.0-pre.10","1.0.0-pre.11","1.0.0-pre.12","1.0.0-pre.13","1.0.0-pre.14","1.0.0-pre.15","1.0.0-pre.16","1.0.0-pre.17","1.0.0-pre.18","1.0.0-pre.2","1.0.0-pre.3","1.0.0-pre.4","1.0.0-pre.5","1.0.0-pre.6","1.0.0-pre.7","1.0.0-pre.8","1.0.0-pre.9","1.1.0","1.1.1","1.1.2","1.1.3","1.10.0","1.10.1","1.10.2","1.10.3","1.10.4","1.11.0","1.11.1","1.12.0","1.12.1","1.12.2","1.12.3","1.12.4","1.2.0","1.2.1","1.2.2","1.2.3","1.3.0","1.4.0","1.4.1","1.4.2","1.5.0","1.5.1","1.5.2","1.5.3","1.5.4","1.5.5","1.5.6","1.5.7","1.6.0","1.6.1","1.6.10","1.6.11","1.6.2","1.6.3","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.7.0","1.8.0","1.9.0"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-74836.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/mtrudel/bandit","events":[{"introduced":"6feadb31189d18b7dcda6c663112cd3bbaf63a46"},{"fixed":"f6914aad14bb1365dd6f306aa592cfb0819bed3e"}]}],"versions":["1.12.4","1.12.3","1.12.1","1.12.0","1.11.1","1.11.0","1.10.4","1.10.3","1.10.2","1.10.1","1.10.0","1.9.0","1.8.0","1.7.0","1.6.11","1.6.10","1.6.9","1.6.8","1.6.7","1.6.6","1.6.5","1.6.4","1.6.3","1.6.2","1.6.1","1.6.0","1.5.7","1.5.6","1.5.5","1.5.4","1.5.3","1.5.2","1.5.1","1.5.0","1.4.2","1.4.1","1.4.0","1.3.0","1.2.3","1.2.0","1.1.3","1.1.2","1.1.1","1.1.0","1.0.0","1.0.0-pre.18","1.0.0-pre.17","1.0.0-pre.16","1.0.0-pre.15","1.0.0-pre.14","1.0.0-pre.13","1.0.0-pre.12","1.0.0-pre.11","1.0.0-pre.10","1.0.0-pre.9","1.0.0-pre.8","1.0.0-pre.7","1.0.0-pre.6","1.0.0-pre.5","1.0.0-pre.4","1.0.0-pre.3","1.0.0-pre.2","1.0.0-pre.1","0.7.7","0.7.6","0.7.5","0.7.4","0.7.3","0.7.2","0.7.1","0.7.0","0.6.11","0.6.10","0.6.9","0.6.8","0.6.7","0.6.6","0.6.5","0.6.4","0.6.3","0.6.2","0.6.1","0.6.0","0.5.11","0.5.10","0.5.9","0.5.8","0.5.7","0.5.6","0.5.5","0.5.4","0.5.3","0.5.2","0.5.1","0.5.0","0.4.10","0.4.9","0.4.8","0.4.7","0.4.6","0.4.5","0.4.4","0.4.3","0.4.2","0.4.1","0.4.0","0.3.9","0.3.8","0.3.7","0.3.6","0.3.5","0.3.4"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-74836.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}],"credits":[{"name":"Giovanni Visciano / Hewlett Packard Enterprise - Athonet","type":"REPORTER"},{"name":"Mat Trudel","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen / EEF","type":"COORDINATOR"}]}