CVE-2026-55619 eml_parser: Parser DoS via deeply nested parentheses in e-mail headers
Attackers can cause denial of service in applications using eml_parser by submitting emails with deeply nested parentheses, crashing the parser.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-55619?
CVE-2026-55619 is a medium-severity denial of service vulnerability in GOVCERT-LU eml_parser, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
eml_parser serves as a python module for parsing eml files and returning various information found in the e-mail as well as computed information. Prior to 3.0.2, eml_parser.parser.HeaderParser.header_fetch_parse in eml_parser/parser.py uses email.utils.getaddresses() to parse address-bearing e-mail headers. A deeply nested CFWS comment construct exhausts the standard-library recursive descent parser's call stack and raises RecursionError, which is not caught and therefore aborts parsing of the entire message. An attacker can disrupt SOC pipelines that process untrusted EML files, although callers already need to handle exceptions from malformed or pathological messages. This issue is fixed in version 3.0.2.
Which versions are affected by CVE-2026-55619?
3 open source packages ship an affected version, including eml_parser and eml-parser.
| Package | Affected | Fixed in |
|---|---|---|
eml_parser PyPI | All versions | 3.0.2 |
eml-parser PyPI | All versions | 3.0.2 |
eml-parser PyPI | All versions | 3.0.2 |
How do I fix CVE-2026-55619?
Upgrade eml_parser to 3.0.2 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-55619 being exploited?
There is no known exploitation of CVE-2026-55619 in the wild and no public exploit code.
Sources
Also known as GHSA-m66c-fw79-6359, PYSEC-2026-3833.