How severe is CVE-2021-28661?

CVE-2021-28661 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-2021-28661?

CVE-2021-28661 affects the following packages: silverstripe/graphql (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-28661?

Update silverstripe/graphql to 3.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-28661 is resolved across your whole dependency graph.

How do I detect CVE-2021-28661 in my Packagist dependencies?

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

How do I mitigate CVE-2021-28661 if there is no patch (or I can't update yet)?

Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Is CVE-2021-28661 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2021-28661, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-28661?

CVE-2021-28661 has an EPSS (Exploit Prediction Scoring System) score of 0.8%, placing it in the 57th 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-2021-28661?

CVE-2021-28661 is classified as CWE-863 (CWE-863). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-28661 published, and has it been updated?

CVE-2021-28661 was published on October 7, 2021 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-2021-28661 — graphql

MEDIUMFix: silverstripe/silverstripe-graphql#407

CVE-2021-28661 is a medium-severity (CVSS 4.3) CWE-863 vulnerability in silverstripe/graphql. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for silverstripe/graphql — see the affected versions and patch details below.

SilverStripe GraphQL Server permission checker not inherited by query subclass.

Also known asBIT-silverstripe-2021-28661GHSA-r7rh-g777-g5gx

Published

Oct 7, 2021

Updated

Oct 24, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

1 known

Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

0.8%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs57th percentile — riskier than 57% 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

1 pkg affected

🐘silverstripe/graphql

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

Default SilverStripe GraphQL Server (aka silverstripe/graphql) 3.x through 3.4.1 permission checker not inherited by query subclass.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`silverstripe/graphql`	≥ 3.0.0&&< 3.5.2	3.5.2`composer require silverstripe/graphql:^3.5.2`

Affected Products

1 product · 1 configurations

Application

silverstripesilverstripe

≥ 3.0.0 && ≤ 3.4.1

range

Exploits & PoCs

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

Default SilverStripe GraphQL Server (aka silverstripe/graphql) 3.x throu…

silverstripe.orgNVDOct 2021

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for silverstripe/graphql, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update silverstripe/graphql to 3.5.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-28661 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

Default SilverStripe GraphQL Server (aka silverstripe/graphql) 3.x through 3.4.1 permission checker not inherited by query subclass.

O3 Security · Impact-Aware SCA

Is CVE-2021-28661 in your dependencies?

Find it across Packagist, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

4.3/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

CWE Classification

CWE-863CWE-863

Weaponization

No Nuclei template or Metasploit module yet. 1 public proof-of-concept reference is listed on this page.

Timeline

Disclosed

Oct 7, 2021

First exploit

Oct 15, 2021

7 days after disclosure — rapid exploitation

Last updated

Oct 24, 2026

Identifiers

CVE-2021-28661

GHSA-r7rh-g777-g5gx

BIT-silverstripe-2021-28661

References

Advisorygithub.com · releases Advisorynvd.nist.gov · CVE 2021 28661 Webgithub.com · 16961459f681f7b32145296189dfdbcc7715e6ed Webgithub.com · CVE 2021 28661.yaml Webgithub.com · 3.5.2 Packagegithub.com · silverstripe graphql Evidencesilverstripe.org · CVE 2021 28661

Related vulnerabilities

Also affects silverstripe/graphql

This CVE is medium severity; 7 of 7 other CVEs affecting silverstripe/graphql are rated as high or higher (top: high).

GHSA-wjg9-v8cf-f5q2CVE-2023-44401CVE-2023-40180CVE-2023-28104CVE-2020-6165CVE-2019-12437CVE-2020-26136

Same weakness: CWE-863

This CVE is medium severity; 1 of 1 other CVE with CWE-863 is rated as high or higher (top: high).

CVE-2026-114146Browse all CWE-863

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 24, 2026

CVE-2021-28661 — graphql

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Frequently Asked Questions

Is CVE-2021-28661 in your dependencies?