{"id":"PYSEC-2026-3833","summary":"eml_parser has 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.","aliases":["CVE-2026-55619","GHSA-m66c-fw79-6359"],"modified":"2026-09-10T12:15:06.893976732Z","published":"2026-09-10T09:44:56.704523Z","references":[{"type":"WEB","url":"https://github.com/GOVCERT-LU/eml_parser/security/advisories/GHSA-m66c-fw79-6359"},{"type":"WEB","url":"https://github.com/GOVCERT-LU/eml_parser/pull/90"},{"type":"WEB","url":"https://github.com/GOVCERT-LU/eml_parser/commit/746a69f86443eb0b6a47f77db3cfe727c21f92b3"},{"type":"PACKAGE","url":"https://github.com/GOVCERT-LU/eml_parser"},{"type":"WEB","url":"https://github.com/GOVCERT-LU/eml_parser/releases/tag/v3.0.2"},{"type":"PACKAGE","url":"https://pypi.org/project/eml-parser"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-m66c-fw79-6359"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55619"}],"affected":[{"package":{"name":"eml-parser","ecosystem":"PyPI","purl":"pkg:pypi/eml-parser"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.0.2"}]}],"versions":["0.9","1.0","1.1","1.10","1.11","1.11.1","1.11.2","1.11.4","1.11.5","1.11.6","1.11.7","1.12.0","1.13.0","1.14.0","1.14.1","1.14.2","1.14.3","1.14.4","1.14.5","1.14.6","1.14.7","1.14.8","1.15.0","1.16.0","1.17.0","1.17.1","1.17.2","1.17.3","1.17.4","1.17.5","1.3","1.4","1.5","1.6","1.7","1.8","1.9","2.0.0","2.0.1","3.0.0","3.0.1"],"database_specific":{"source":"https://github.com/pypa/advisory-database/blob/main/vulns/eml-parser/PYSEC-2026-3833.yaml"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"}]}