How severe is CVE-2020-5218?

CVE-2020-5218 has a CVSS score of 4.3/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2020-5218?

CVE-2020-5218 affects the following packages: sylius/resource-bundle (Packagist), sylius/resource-bundle (Packagist), sylius/resource-bundle (Packagist), sylius/sylius (Packagist), sylius/sylius (Packagist), sylius/resource-bundle (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2020-5218?

Update sylius/resource-bundle to 1.4.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5218 is resolved across your whole dependency graph.

How do I detect CVE-2020-5218 in my Packagist dependencies?

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

How do I mitigate CVE-2020-5218 if there is no patch (or I can't update yet)?

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.

Is CVE-2020-5218 actively exploited in the wild?

No public exploit code has been indexed for CVE-2020-5218 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-2020-5218?

CVE-2020-5218 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 48th 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-2020-5218?

CVE-2020-5218 is classified as CWE-444 (CWE-444). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2020-5218 published, and has it been updated?

CVE-2020-5218 was published on January 27, 2020 and was last updated on October 24, 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

MEDIUM severity

CVE-2020-5218 — resource-bundle

MEDIUM

CVE-2020-5218 is a medium-severity (CVSS 4.3) CWE-444 vulnerability in sylius/resource-bundle. A fix is available for sylius/resource-bundle — see the affected versions and patch details below.

Ability to expose data in Sylius by using an unintended serialisation group

Also known asCVE-2020-5220 GHSA-8vp7-j5cj-vvm2 GHSA-prg5-hg25-8grq

Published

Jan 27, 2020

Updated

Oct 24, 2026

Affected

6 pkgs

Patched

6 / 6

Exploits

None indexed

Exploitation data as of Oct 25, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs48th percentile — riskier than 48% of all scored CVEsHighest risk

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

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

6 pkgs affected

🐘sylius/resource-bundle🐘sylius/resource-bundle🐘sylius/resource-bundle🐘sylius/sylius🐘sylius/sylius🐘sylius/resource-bundle

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

ResourceBundle accepts and uses any serialisation groups to be passed via a HTTP header. This might lead to data exposure by using an unintended serialisation group - for example it could make Shop API use a more permissive group from Admin API.

Anyone exposing an API with ResourceBundle's controller is affected. The vulnerable versions are: <1.3 || >=1.3.0 <=1.3.12 || >=1.4.0 <=1.4.5 || >=1.5.0 <=1.5.0 || >=1.6.0 <=1.6.2.

Patches

The patch is provided for ResourceBundle 1.3.13, 1.4.6, 1.5.1 and 1.6.3, but not for any versions below 1.3.

After it is applied, It allows to choose only the groups that are defined in serialization_groups or allowed_serialization_groups route definition. Any group not defined in those will not be used.

This behaviour might be a BC break for those using custom groups via the HTTP header, please adjust allowed_serialization_groups accordingly.

Workarounds

Service sylius.resource_controller.request_configuration_factory can be overridden with an implementation copied from \Sylius\Bundle\ResourceBundle\Controller\RequestConfigurationFactory where the part that handles custom serialisation groups is deleted.

Affected Packages

6 total 6 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`sylius/resource-bundle`	≥ 1.4.0&&< 1.4.6	1.4.6`composer require sylius/resource-bundle:^1.4.6`
🐘Packagist	`sylius/resource-bundle`	≥ 1.5.0&&< 1.5.1	1.5.1`composer require sylius/resource-bundle:^1.5.1`
🐘Packagist	`sylius/resource-bundle`	≥ 1.6.0&&< 1.6.3	1.6.3`composer require sylius/resource-bundle:^1.6.3`
🐘Packagist	`sylius/sylius`	all versions	1.3.12`composer require sylius/sylius:^1.3.12`
🐘Packagist	`sylius/sylius`	≥ 1.4.0&&< 1.4.4	1.4.4`composer require sylius/sylius:^1.4.4`
🐘Packagist	`sylius/resource-bundle`	≥ 1.0.0&&< 1.3.13	1.3.13`composer require sylius/resource-bundle:^1.3.13`

Affected Products

1 product · 4 configurations

Application

syliussylius

≥ 1.6.0 && < 1.6.3

1 version

1.5.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for sylius/resource-bundle, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update sylius/resource-bundle to 1.4.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-5218 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

### Impact ResourceBundle accepts and uses any serialisation groups to be passed via a HTTP header. This might lead to data exposure by using an unintended serialisation group - for example it could make Shop API use a more permissive group from Admin API. Anyone exposing an API with ResourceBundle's controller is affected. The vulnerable versions are: `<1.3 || >=1.3.0 <=1.3.12 || >=1.4.0 <=1.4.5 || >=1.5.0 <=1.5.0 || >=1.6.0 <=1.6.2`. ### Patches The patch is provided for ResourceBundle 1.3.13, 1.4.6, 1.5.1 and 1.6.3, but not for any versions below 1.3. After it is applied, It allows to