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Not in CISA KEV
HIGH severity

CVE-2020-23478 — leo

HIGHFix: leo-editor/leo-editor@0298336

CVE-2020-23478 is a high-severity (CVSS 7.5) CWE-697 vulnerability in leo. 1 public exploit reference exists, so weaponization risk is real. A fix is available for leo — see the affected versions and patch details below.

Regular Expression Denial of Service in Leo Editor

Also known asGHSA-x38q-xg2h-rxgxPYSEC-2021-338
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
1 known
Exploitation data as of Oct 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs68th percentile — riskier than 68% of all scored CVEsHighest risk
0.73%1.07%1.40%1.73%1.2%1.2%Oct 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2020-23478 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

1 pkg affected
🐍leo

Real-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

Leo Editor v6.2.1 was discovered to contain a regular expression denial of service (ReDoS) vulnerability in the component plugins/importers/dart.py.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐍PyPIleoall versions6.3pip install --upgrade 'leo==6.3'

Affected Products

1 product · 1 configurations
Application
leoleoeditor
1 version
6.2.1
Exploits & PoCs
1

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Leo Editor v6.2.1 was discovered to contain a regular expression denial …

github.comNVDSep 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for leo, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update leo to 6.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-23478 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

Leo Editor v6.2.1 was discovered to contain a regular expression denial of service (ReDoS) vulnerability in the component plugins/importers/dart.py.
O3 Security · Impact-Aware SCA

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CVE-2020-23478: leo DoS — Fixed in 6.3