CVE-2026-49754: mint Unbounded CONTINUATION/HEADERS Frame Accumulation (CONTINUATION Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-2p26-p43x-fhp8",
  "modified" : "2026-07-09T23:19:23Z",
  "published" : "2026-07-09T23:19:23Z",
  "aliases" : [ "CVE-2026-49754" ],
  "summary" : "mint: Unbounded CONTINUATION/HEADERS frame accumulation (CONTINUATION flood)",
  "details" : "### Summary\n\nMint's HTTP/2 client accumulates `CONTINUATION` header-block fragments into a per-connection buffer with no cap on size or frame count. A malicious or compromised HTTP/2 server can drive the client's memory to arbitrary size by streaming an endless chain of `CONTINUATION` frames after a `HEADERS` frame that omits `END_HEADERS`, causing memory exhaustion and BEAM process death. A single connection to an attacker-controlled HTTP/2 endpoint is sufficient.\n\n### Details\n\nWhen Mint's HTTP/2 receive path observes a `HEADERS` frame without the `END_HEADERS` flag, `'Elixir.Mint.HTTP2':handle_headers/3` parks the unparsed header-block fragment in `conn.headers_being_processed`. Every subsequent `CONTINUATION` frame on that stream is then appended to the accumulator by `'Elixir.Mint.HTTP2':handle_continuation/3`.\n\nNothing in the receive path bounds this accumulator: there is no per-stream size cap, no `CONTINUATION` frame-count cap, and `max_header_list_size` is only enforced on outgoing requests (its default is `:infinity`, and the only enforcement helper inspects `server_settings` for request encoding, never inbound header blocks). Each `CONTINUATION` payload can be up to the peer-advertised `SETTINGS_MAX_FRAME_SIZE`, so the attacker can grow `headers_being_processed` to arbitrary size at line rate.\n\n### PoC\n\n1. Stand up a raw TCP server that speaks the HTTP/2 handshake.\n2. After the client's request `HEADERS` arrives, respond with a `HEADERS` frame on stream 1 with `flags = 0` (no `END_HEADERS`, no `END_STREAM`) and an empty header-block fragment.\n3. Stream `CONTINUATION` frames on stream 1, each with `flags = 0` and a payload up to `SETTINGS_MAX_FRAME_SIZE`. Never set `END_HEADERS`.\n4. The client's process memory grows linearly with the flood 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. A single connection is sufficient to drive memory to arbitrary size and crash the BEAM process. The default Mint configuration is vulnerable; no client-side opt-in is required. Scored CVSS v4.0 8.2 (HIGH).\n\n## Workarounds\n\nRestrict Mint to HTTP/1 on connections to untrusted servers by passing `protocols: [:http1]` to `'Elixir.Mint.HTTP':connect/4`. This avoids the vulnerable HTTP/2 receive path entirely, at the cost of losing HTTP/2 for those connections.\n\n## Resources\n\n* Introduction commit: https://github.com/elixir-mint/mint/commit/596ca4304504be68939c4929e0831557097962b8\n* Patch commit: https://github.com/elixir-mint/mint/commit/b662d127d3028b5426c88d4c9cc7fe430491a10b",
  "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"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Hex",
      "name" : "mint"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.9.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/elixir-mint/mint/security/advisories/GHSA-2p26-p43x-fhp8"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-49754"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/elixir-mint/mint/commit/b662d127d3028b5426c88d4c9cc7fe430491a10b"
  }, {
    "type" : "WEB",
    "url" : "https://cna.erlef.org/cves/CVE-2026-49754.html"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/elixir-mint/mint"
  }, {
    "type" : "WEB",
    "url" : "https://osv.dev/vulnerability/EEF-CVE-2026-49754"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-09T23:19:23Z",
    "nvd_published_at" : "2026-06-02T16:16:44Z"
  }
}