---
id: CVE-2026-55619
aliases:
  - GHSA-m66c-fw79-6359
  - PYSEC-2026-3833
title: eml_parser has parser DoS via deeply nested parentheses in e-mail headers
summary: eml_parser has parser DoS via deeply nested parentheses in e-mail headers
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
vendor: eml-parser
product: eml-parser
ecosystem: pip
affected:
  - eml-parser < 3.0.2
patched:
  - eml-parser 3.0.2
published: '2026-08-25'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T12:25:57.609576367Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-m66c-fw79-6359'
references:
  - url: >-
      https://github.com/GOVCERT-LU/eml_parser/security/advisories/GHSA-m66c-fw79-6359
  - url: 'https://github.com/GOVCERT-LU/eml_parser/pull/90'
  - url: >-
      https://github.com/GOVCERT-LU/eml_parser/commit/746a69f86443eb0b6a47f77db3cfe727c21f92b3
  - url: 'https://github.com/GOVCERT-LU/eml_parser'
  - url: 'https://github.com/GOVCERT-LU/eml_parser/releases/tag/v3.0.2'
  - url: 'https://pypi.org/project/eml-parser'
  - url: 'https://github.com/advisories/GHSA-m66c-fw79-6359'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-55619'
tags:
  - osv
  - pip
  - nvd
  - ghsa
epss: 0.00524
epssPercentile: 0.4199
cwe:
  - CWE-770
  - CWE-1124
ingestedAt: '2026-08-25T18:30:21.038Z'
---

## Overview

### Summary

`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 packages

- `eml-parser < 3.0.2`

## Remediation

Upgrade to a patched release:

- `eml-parser 3.0.2`