How severe is CVE-2020-35124?

CVE-2020-35124 has a CVSS score of 9.6/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2020-35124?

CVE-2020-35124 affects the following packages: mautic/core (Packagist), mautic/core (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2020-35124?

Update mautic/core to 3.2.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-35124 is resolved across your whole dependency graph.

How do I detect CVE-2020-35124 in my Packagist dependencies?

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

How do I mitigate CVE-2020-35124 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2020-35124 actively exploited in the wild?

No public exploit code has been indexed for CVE-2020-35124 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2020-35124?

CVE-2020-35124 has an EPSS (Exploit Prediction Scoring System) score of 2.4%, placing it in the 84th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2020-35124?

CVE-2020-35124 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2020-35124 published, and has it been updated?

CVE-2020-35124 was published on January 28, 2021 and was last updated on August 7, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

CRITICAL severity

CVE-2020-35124 — core

CRITICALFix: mautic/mautic@20c5dc3

CVE-2020-35124 is a critical-severity (CVSS 9.6) Cross-site Scripting (XSS) vulnerability in mautic/core. A fix is available for mautic/core — see the affected versions and patch details below.

XSS vulnerability leveraged through referrers could allow un-authorized admin access in Mautic

Also known asGHSA-39wj-j3jc-858m

Published

Jan 28, 2021

Updated

Aug 7, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

2.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs84th percentile — riskier than 84% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2020-35124 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected

🐘mautic/core🐘mautic/core

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Impact

This is a cross-site scripting vulnerability which affects every version of Mautic and could allow an attacker unauthorised administrator level access to Mautic.

This vulnerability was reported by Naveen Sunkavally at Horizon3.ai.

Patches

Upgrade to 3.2.4 or 2.16.5.

Link to patch for 2.x versions: https://github.com/mautic/mautic/compare/2.16.4...2.16.5.diff

Link to patch for 3.x versions: https://github.com/mautic/mautic/compare/3.2.2...3.2.4.diff

Workarounds

None

For more information

If you have any questions or comments about this advisory:

Post in https://forum.mautic.org/c/support
Email us at [email protected]

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`mautic/core`	≥ 3.0.0&&< 3.2.4	3.2.4`composer require mautic/core:^3.2.4`
🐘Packagist	`mautic/core`	≥ 2.0.0&&< 2.16.5	2.16.5`composer require mautic/core:^2.16.5`

Affected Products

1 product · 1 configurations

Application

mauticacquia

< 3.2.4

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for mautic/core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update mautic/core to 3.2.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-35124 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

### Impact This is a cross-site scripting vulnerability which affects every version of Mautic and could allow an attacker unauthorised administrator level access to Mautic. This vulnerability was reported by Naveen Sunkavally at Horizon3.ai. ### Patches Upgrade to 3.2.4 or 2.16.5. Link to patch for 2.x versions: https://github.com/mautic/mautic/compare/2.16.4...2.16.5.diff Link to patch for 3.x versions: https://github.com/mautic/mautic/compare/3.2.2...3.2.4.diff ### Workarounds None ### For more information If you have any questions or comments about this advisory: * Post in https://for