GHSA-Q8X4-X7MP-5VG2

Vulnerability from github – Published: 2026-05-05 21:46 – Updated: 2026-05-05 21:46
VLAI
Summary
Plug.Cowboy vulnerable to unauthenticated remote DoS via HTTP/2 `:scheme` atom-table exhaustion
Details

Summary

An unauthenticated remote denial-of-service vulnerability in Plug.Cowboy.Conn allows any attacker who can reach an HTTPS Plug.Cowboy listener via HTTP/2 to permanently exhaust the BEAM atom table and crash the entire Erlang VM.

Am I Affected?

All users running plug_cowboy with HTTP/2 may be affected, this includes Phoenix applications. If another HTTP adapter such as Bandit is used, then the consuming project is not affected. If the HTTP/2 endpoint is exposed directly (without a proxy) then the project will be affected. If a proxy is in use then it depends on the proxy configuration. Many proxies use HTTP/1.1 internally, and would be unaffected.

Impact

The vulnerability will allow crashing the Erlang VM (BEAM) via atom exhaustion.

Mitigation

Users are advised to update to plug_cowboy v2.8.1 to mitigate this issue.

Credits

Plug.Cowboy thanks Peter Ullrich for finding and responsibly disclosing this vulnerability.

Severity
8.7 (High)
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
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Hex",
        "name": "plug_cowboy"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.8.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-32688"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-05-05T21:46:09Z",
    "nvd_published_at": "2026-04-27T14:16:47Z",
    "severity": "HIGH"
  },
  "details": "## Summary\n\nAn unauthenticated remote denial-of-service vulnerability in `Plug.Cowboy.Conn` allows any attacker who can reach an HTTPS Plug.Cowboy listener via HTTP/2 to permanently exhaust the BEAM atom table and crash the entire Erlang VM.\n\n## Am I Affected?\n\nAll users running plug_cowboy with HTTP/2 may be affected, this includes Phoenix applications. If another HTTP adapter such as Bandit is used, then the consuming project is not affected. If the HTTP/2 endpoint is exposed directly (without a proxy) then the project will be affected. If a proxy is in use then it depends on the proxy configuration. Many proxies use HTTP/1.1 internally, and would be unaffected.\n\n## Impact\n\nThe vulnerability will allow crashing the Erlang VM (BEAM) via atom exhaustion.\n\n## Mitigation\n\nUsers are advised to update to plug_cowboy v2.8.1 to mitigate this issue.\n\n## Credits\nPlug.Cowboy thanks Peter Ullrich for finding and responsibly disclosing this vulnerability.",
  "id": "GHSA-q8x4-x7mp-5vg2",
  "modified": "2026-05-05T21:46:09Z",
  "published": "2026-05-05T21:46:09Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/elixir-plug/plug_cowboy/security/advisories/GHSA-q8x4-x7mp-5vg2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-32688"
    },
    {
      "type": "WEB",
      "url": "https://github.com/elixir-plug/plug_cowboy/commit/bfb34cb45eb354e56437f7023fb306de1bf9c19b"
    },
    {
      "type": "WEB",
      "url": "https://cna.erlef.org/cves/CVE-2026-32688.html"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/elixir-plug/plug_cowboy"
    },
    {
      "type": "WEB",
      "url": "https://osv.dev/vulnerability/EEF-CVE-2026-32688"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "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",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Plug.Cowboy vulnerable to unauthenticated remote DoS via HTTP/2 `:scheme` atom-table exhaustion"
}


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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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