GHSA-JRPM-956J-96JG

Vulnerability from github – Published: 2026-09-15 20:01 – Updated: 2026-09-15 20:01
VLAI
Summary
Http4s: Ember chunk parser lenience (TE.TE request smuggling)
Details

Summary

Ember's chunk decoder parses the size token leniently: it strips leading and trailing whitespace and accepts a leading + or - sign. RFC9112 §7.1 defines chunk-size = 1*HEXDIG. An intermediary that parses the chunk boundary differently (or rejects it) will disagree with Ember on request framing, enabling HTTP request smuggling (TE.TE).

Impact

Server

Request smuggling (TE.TE) when ember-server is an origin behind an intermediary that forwards the body verbatim but interprets the malformed chunk sizes differently

  • Front-end security bypass: the smuggled request reaches paths the intermediary might have blocked, with attacker-chosen method and headers.
  • Cache poisoning: the smuggled response is associated with the next request key in a caching proxy.
  • Request queue hijack:

Client

ember-client has the same leniencies on the response path, which enables response smuggling when http4s is used as a gateway. This is less severe, as it requires a malicious or compromised upstream rather than an anonymous remote client.

Preconditions

  • Unauthenticated remote attacker (server)
  • ember-server as origin behind a keep-alive intermediary
  • Malicious or compromised upstream (client)
  • Intermediary or upstream forwards chunked bodies without re-encoding and disagrees with Ember on + prefix, - prefix, or leading and trailing octets rather than rejecting.

Workarounds

  • Intermediary strictly rejects malformed chunk sizes
  • Intermediary buffers and re-encodes request bodies

References

Severity
5.4 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.34"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-ember-core_2.12"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.34"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-ember-core_2.13"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.23.34"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-ember-core_3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.23.35"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.0.0-M46"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-ember-core_2.13"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0-M1"
            },
            {
              "fixed": "1.0.0-M47"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 1.0.0-M46"
      },
      "package": {
        "ecosystem": "Maven",
        "name": "org.http4s:http4s-ember-core_3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0-M1"
            },
            {
              "fixed": "1.0.0-M47"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-69216"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-444"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-15T20:01:00Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nEmber\u0027s chunk decoder parses the size token leniently: it strips leading and trailing whitespace and accepts a leading `+` or `-` sign.  RFC9112 \u00a77.1 defines `chunk-size = 1*HEXDIG`.  An intermediary that parses the chunk boundary differently (or rejects it) will disagree with Ember on request framing, enabling HTTP request smuggling (TE.TE).\n\n## Impact\n\n### Server\n\nRequest smuggling (TE.TE) when ember-server is an origin behind an intermediary that forwards the body verbatim but interprets the malformed chunk sizes differently\n\n- Front-end security bypass: the smuggled request reaches paths the intermediary might have blocked, with attacker-chosen method and headers.\n- Cache poisoning: the smuggled response is associated with the next request key in a caching proxy.\n- Request queue hijack:\n\n### Client\n\nember-client has the same leniencies on the response path, which enables response smuggling when http4s is used as a gateway.  This is less severe, as it requires a malicious or compromised upstream rather than an anonymous remote client.\n\n## Preconditions\n\n- Unauthenticated remote attacker (server)\n- ember-server as origin behind a keep-alive intermediary\n- Malicious or compromised upstream (client)\n- Intermediary or upstream forwards chunked bodies without re-encoding and disagrees with Ember on `+` prefix, `-` prefix, or leading and trailing octets rather than rejecting.\n\n## Workarounds\n\n- Intermediary strictly rejects malformed chunk sizes\n- Intermediary buffers and re-encodes request bodies\n\n## References\n\n- [RFC9112 \u00a77.1: Chunked Transfer Coding](https://www.rfc-editor.org/rfc/rfc9112.html#name-chunked-transfer-coding)",
  "id": "GHSA-jrpm-956j-96jg",
  "modified": "2026-09-15T20:01:00Z",
  "published": "2026-09-15T20:01:00Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/http4s/http4s/security/advisories/GHSA-jrpm-956j-96jg"
    },
    {
      "type": "WEB",
      "url": "https://github.com/http4s/http4s/commit/d78612a5abd5a2547487598d3342be05573e16f0"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/http4s/http4s"
    },
    {
      "type": "WEB",
      "url": "https://github.com/http4s/http4s/releases/tag/v0.23.35"
    },
    {
      "type": "WEB",
      "url": "https://github.com/http4s/http4s/releases/tag/v1.0.0-M47"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Http4s: Ember chunk parser lenience (TE.TE request smuggling)"
}



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