{
  "affected": [
    {
      "ranges": [
        {
          "database_specific": {
            "extracted_events": [
              {
                "introduced": "0"
              },
              {
                "fixed": "7.22"
              }
            ],
            "source": [
              "AFFECTED_FIELD",
              "REFERENCES"
            ]
          },
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "a9df523f76f43a38bd53b4232b9cfd4c16869e71"
            },
            {
              "fixed": "beb73a65a99619ff349c59037ea5197f27c7e533"
            }
          ],
          "repo": "https://github.com/cesanta/mongoose",
          "type": "GIT"
        }
      ]
    }
  ],
  "aliases": [
    "GHSA-mgp5-rjrv-h5j3"
  ],
  "database_specific": {
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
      "CWE-444"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73256.json"
  },
  "details": "Mongoose is an embedded web server and network library. Prior to 7.22, a remote unauthenticated attacker can exploit an HTTP/1.0 reverse-proxy deployment by sending a request with Transfer-Encoding: chunked and conflicting framing. The http_cb() function in src/http.c tests hm.proto.len with an impossible greater-than-eight condition even though mg_http_parse() requires an eight-byte protocol string, so is_http_1_0 is never set. Mongoose consequently processes chunked encoding that an HTTP/1.0 proxy can ignore, enabling request smuggling and unauthorized access or state changes. This issue is fixed in version 7.22.",
  "id": "CVE-2026-73256",
  "modified": "2026-08-23T03:42:28.307043686Z",
  "published": "2026-08-20T17:37:54.505Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/cesanta/mongoose/releases/tag/7.22"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/73xxx/CVE-2026-73256.json"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/cesanta/mongoose/security/advisories/GHSA-mgp5-rjrv-h5j3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-73256"
    },
    {
      "type": "FIX",
      "url": "https://github.com/cesanta/mongoose/commit/a9df523f76f43a38bd53b4232b9cfd4c16869e71"
    },
    {
      "type": "FIX",
      "url": "https://github.com/cesanta/mongoose/pull/3611"
    }
  ],
  "schema_version": "1.9.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mongoose: HTTP/1.0 detection off-by-one enables request smuggling via chunked TE"
}