{"id":"GHSA-g586-ccqf-7x4r","summary":"mint: Unbounded streams map growth via PUSH_PROMISE without follow-up HEADERS","details":"### Summary\n\nMint's HTTP/2 client accepts `PUSH_PROMISE` frames from any server it connects to and inserts every promised stream into a per-connection map without consulting `max_concurrent_streams`. A malicious or compromised HTTP/2 server can flood the client with `PUSH_PROMISE` frames and withhold the matching response `HEADERS`, pinning one map entry per frame indefinitely until the client process runs out of memory.\n\n### Details\n\n`'Elixir.Mint.HTTP2':handle_push_promise/3` in `lib/mint/http2.ex` dispatches every inbound `PUSH_PROMISE` frame to `'Elixir.Mint.HTTP2':decode_push_promise_headers_and_add_response/5`, which inserts a `:reserved_remote` entry into `conn.streams` for the promised ID. The only validation applied is that the promised ID is even and not already present; `client_settings.max_concurrent_streams` is not consulted at promise time.\n\nThe concurrency cap is only checked when the response `HEADERS` for the promised stream arrive. A server that emits `PUSH_PROMISE` frames and never sends the matching `HEADERS` never trips that check, and the existing tally counts only streams in open states, not `:reserved_remote` entries.\n\nHTTP/2 server push is accepted by default (`client_settings.enable_push` defaults to `true`), so no application opt-in is required. A single long-lived HTTP/2 connection to a hostile server lets it pin one `conn.streams` entry per `PUSH_PROMISE` frame, with no upper bound.\n\n### PoC\n\n1. Stand up a raw TCP HTTP/2 server that completes the handshake and ACKs the client's `SETTINGS`.\n2. Wait for the client's request `HEADERS` and capture its odd stream ID.\n3. Send a flood of `PUSH_PROMISE` frames (`flags = END_HEADERS`) associated with the captured stream, each promising a fresh even stream ID and carrying a minimal HPACK-encoded header block.\n4. Never send the matching response `HEADERS` for any of the promised IDs.\n5. The client's `conn.streams` map grows by one entry per `PUSH_PROMISE` frame (~148 bytes/entry); memory grows linearly and the BEAM process eventually crashes with OOM.\n\n### Impact\n\nRemote, unauthenticated denial-of-service against any process using Mint as an HTTP/2 client against an untrusted or attacker-influenced server. Server push is on by default, so no application code change can prevent it short of disabling push or upgrading. Affected populations include outbound HTTP/2 clients in web backends, webhook delivery systems, scrapers, federated and proxy components, and any service that follows redirects to third-party HTTP/2 origins.\n\n## Workarounds\n\nDisable HTTP/2 server push on connections to untrusted servers by passing `client_settings: [enable_push: false]` to `'Elixir.Mint.HTTP':connect/4`. Mint will then reject any inbound `PUSH_PROMISE` frame with a `PROTOCOL_ERROR` before the vulnerable code path is reached.\n\n## Resources\n\n* Introduction commit: https://github.com/elixir-mint/mint/commit/65c6394d05a1b8aa4a7461708c3aa173e8d7a5cf\n* Patch commit: https://github.com/elixir-mint/mint/commit/70b97b6a5209fb288b0e04d8e657dda26c59de67","aliases":["CVE-2026-48862","EEF-CVE-2026-48862"],"modified":"2026-07-09T23:30:09.074431244Z","published":"2026-07-09T23:19:29Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-07-09T23:19:29Z","nvd_published_at":"2026-06-02T16:16:44Z","cwe_ids":["CWE-770"],"severity":"HIGH"},"references":[{"type":"WEB","url":"https://github.com/elixir-mint/mint/security/advisories/GHSA-g586-ccqf-7x4r"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-48862"},{"type":"WEB","url":"https://github.com/elixir-mint/mint/commit/70b97b6a5209fb288b0e04d8e657dda26c59de67"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-48862.html"},{"type":"PACKAGE","url":"https://github.com/elixir-mint/mint"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-48862"}],"affected":[{"package":{"name":"mint","ecosystem":"Hex","purl":"pkg:hex/mint"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0.2.0"},{"fixed":"1.9.0"}]}],"versions":["0.2.0","0.2.1","0.3.0","0.4.0","0.5.0","1.0.0","1.1.0","1.2.0","1.2.1","1.3.0","1.4.0","1.4.1","1.4.2","1.5.0","1.5.1","1.5.2","1.6.0","1.6.1","1.6.2","1.7.0","1.7.1","1.8.0"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/07/GHSA-g586-ccqf-7x4r/GHSA-g586-ccqf-7x4r.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"}]}