{"id":"CVE-2026-55619","aliases":["GHSA-m66c-fw79-6359","PYSEC-2026-3833"],"url":"https://o3.security/vulnerability/CVE-2026-55619","summary":"eml_parser: Parser DoS via deeply nested parentheses in e-mail headers","details":"### Summary\n\n`eml_parser` uses the `email.utils.getaddresses()` function from the CPython standard library to parse e-mail headers that contain e-mail addresses (such as `To`, `Cc`, `Bcc`, `From`, `Reply-To`, `Sender`, ...). When the input header contains a deeply nested CFWS (comment / folding white space) construct, the recursive descent parser in the standard library exhausts the call stack. The resulting `RecursionError` is not caught by `eml_parser`, so the exception propagates and aborts parsing of the whole message.\n\n### Impact\n\nSOC pipelines use `eml_parser` to process untrusted e-mails. An attacker can easily create an eml file that will trigger the `RecursionError` during parsing.\n\nThe impact is mitigated by the fact that there are various other situations in which `eml_parser` will raise an exception when attempting to parse a malformed or pathological eml file. In particular, very deeply nested multipart e-mails also result in a `RecursionError` being raised by the library voluntarily. Therefore, systems relying on `eml_parser` already need to detect and handle errors emanating from the library in an appropriate way.\n\n### Workarounds\n\nThe issue can be avoided by wrapping the call to `eml_parser.decode_email` or `eml_parser.decode_email_bytes` in a `try/except` construct.\n\n### Patches\n\nSince version 3.0.2, `eml_parser` will catch the error in the standard library parser and fall back to a simpler parser based on a regular expression.","published":"2026-08-25T18:24:29.921Z","modified":"2026-09-11T03:30:51.694243598Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},"epss":{"score":0.00302,"percentile":0.22263,"asOf":"2026-08-27"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"eml-parser","fixedVersion":"3.0.2"}],"fix":{"url":"https://github.com/GOVCERT-LU/eml_parser/commit/746a69f86443eb0b6a47f77db3cfe727c21f92b3","label":"GOVCERT-LU/eml_parser@746a69f"},"references":[{"type":"WEB","url":"https://github.com/GOVCERT-LU/eml_parser/releases/tag/v3.0.2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55619.json"},{"type":"ADVISORY","url":"https://github.com/GOVCERT-LU/eml_parser/security/advisories/GHSA-m66c-fw79-6359"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55619"},{"type":"FIX","url":"https://github.com/GOVCERT-LU/eml_parser/commit/746a69f86443eb0b6a47f77db3cfe727c21f92b3"},{"type":"FIX","url":"https://github.com/GOVCERT-LU/eml_parser/pull/90"},{"type":"PACKAGE","url":"https://github.com/GOVCERT-LU/eml_parser"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-09-11T03:30:51.694243598Z"}}