CVE-2026-55618 is a medium-severity (CVSS 6.5) CWE-116 vulnerability in eml-parser. A fix is available for eml-parser — see the affected versions and patch details below.
eml_parser: URL extraction bypass via HTML entities in URLs
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-55618.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-55618 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
eml-parserReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
eml_parser performs certain validations on potential URL strings to discard bogus values. In versions prior to 3.0.2, this validation was performed before unescaping any HTML entities that might occur in the string. This caused the library to wrongfully reject valid URLs that use HTML entities for the :, /, or . characters. These URLs would then not be included in the list of extracted URLs. Similarly, the host parts of such URLs would not be extracted.
For example, neither the URL https://phishing.example.com nor its host (phishing.example.com) would appear in the parsing result.
Impact
eml_parser is used in email security gateways and SOC pipelines to extract URLs as IOCs. Those URLs are then checked against threat-intel feeds, URL reputation services, and sandboxes. A URL that is not extracted is never checked.
Patches
Since version 3.0.2 the library unescapes all HTML entities in every URL before deciding to accept or reject it. A test was added to prevent regressions.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | eml-parser | all versions | 3.0.2pip install --upgrade 'eml-parser==3.0.2' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for eml-parser, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update eml-parser to 3.0.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55618 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Frequently Asked Questions
Is CVE-2026-55618 in your dependencies?
Find it across PyPI, including transitive dependencies.