GHSA-M66C-FW79-6359
Vulnerability from github – Published: 2026-08-25 18:25 – Updated: 2026-08-25 18:25Summary
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.
Impact
SOC pipelines use eml_parser to process untrusted e-mails. An attacker can easily create an eml file that will trigger the RecursionError during parsing.
The 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.
Workarounds
The issue can be avoided by wrapping the call to eml_parser.decode_email or eml_parser.decode_email_bytes in a try/except construct.
Patches
Since 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.
{
"affected": [
{
"package": {
"ecosystem": "PyPI",
"name": "eml_parser"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "3.0.2"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-55619"
],
"database_specific": {
"cwe_ids": [
"CWE-1124",
"CWE-770"
],
"github_reviewed": true,
"github_reviewed_at": "2026-08-25T18:25:47Z",
"nvd_published_at": null,
"severity": "MODERATE"
},
"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.",
"id": "GHSA-m66c-fw79-6359",
"modified": "2026-08-25T18:25:47Z",
"published": "2026-08-25T18:25:47Z",
"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"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
"type": "CVSS_V3"
}
],
"summary": "eml_parser has parser DoS via deeply nested parentheses in e-mail headers"
}
Sightings
| Author | Source | Type | Date | Other |
|---|
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- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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