How severe is CVE-2021-41749?

CVE-2021-41749 has a CVSS score of 9.8/10, rated CRITICAL. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-41749?

CVE-2021-41749 affects the following packages: nystudio107/craft-seomatic (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2021-41749?

Update nystudio107/craft-seomatic to 3.4.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41749 is resolved across your whole dependency graph.

How do I detect CVE-2021-41749 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nystudio107/craft-seomatic, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-41749 if there is no patch (or I can't update yet)?

Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

Is CVE-2021-41749 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-41749 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-2021-41749?

CVE-2021-41749 has an EPSS (Exploit Prediction Scoring System) score of 16.8%, placing it in the 97th 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 warrants monitoring and prompt remediation.

What type of vulnerability is CVE-2021-41749?

CVE-2021-41749 is classified as Code Injection (CWE-94). 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.

Is there exploit tooling available for CVE-2021-41749?

A Nuclei detection template exists for CVE-2021-41749, meaning automated scanners can fingerprint it. Public exploit tooling significantly increases real-world risk — prioritize patching and ensure detection coverage. Exploit tooling should only ever be used in isolated, authorized testing environments.

When was CVE-2021-41749 published, and has it been updated?

CVE-2021-41749 was published on June 12, 2022 and was last updated on October 20, 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-2021-41749 — craft-seomatic

CRITICALFix: nystudio107/craft-seomatic@3fee7d5

CVE-2021-41749 is a critical-severity (CVSS 9.8) Code Injection vulnerability in nystudio107/craft-seomatic. EPSS puts its 30-day exploitation probability at 16.8% (97th percentile). A fix is available for nystudio107/craft-seomatic — see the affected versions and patch details below.

Code Injection in SEOmatic

Also known asGHSA-g7xr-v82w-qggq

Published

Jun 12, 2022

Updated

Oct 20, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 8, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

16.8%probability of exploitation in next 30 days

Moderate Risk0.00%

Lower risk than most CVEs97th percentile — riskier than 97% 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

🐘nystudio107/craft-seomatic

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

In the SEOmatic plugin up to 3.4.11 for Craft CMS 3, it is possible for unauthenticated attackers to perform a Server-Side Template Injection, allowing for remote code execution.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`nystudio107/craft-seomatic`	all versions	3.4.11`composer require nystudio107/craft-seomatic:^3.4.11`

Affected Products

1 product · 1 configurations

Application

seomaticnystudio107

≤ 3.4.11

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for nystudio107/craft-seomatic, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update nystudio107/craft-seomatic to 3.4.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41749 is resolved across your whole dependency graph.
Workarounds
Stop passing untrusted input into the interpreter or shell: call the affected binary with an argument array rather than a composed command string, reject anything outside a strict allowlist of expected values, and run the component under an account that cannot reach beyond the work it legitimately does.

How to detect CVE-2021-41749

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id cve-2021-41749 -u https://target

Template: CraftCMS SEOmatic - Server-Side Template Injection
Severity: critical
Impact: Unauthenticated attackers can exploit SSTI via X-Forwarded-Host header to execute arbitrary Twig templates and system commands, achieving complete server compromise.
Remediation: Upgrade to CraftCMS SEOmatic version 3.4.12 or later.

Template by ProjectDiscovery nuclei-templates (iamnoooob, ritikchaddha), MIT licensed. View the full template. Scan only systems you are authorised to test.

Frequently Asked Questions

In the SEOmatic plugin up to 3.4.11 for Craft CMS 3, it is possible for unauthenticated attackers to perform a Server-Side Template Injection, allowing for remote code execution.

O3 Security · Impact-Aware SCA

Is CVE-2021-41749 in your dependencies?

Find it across Packagist, including transitive dependencies.

Scan my dependencies How O3 SCA works

CVSS Score

9.8/10CVSS v3 base

Vector breakdown

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Raw vector

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

CWE Classification

Weaponization

Timeline

Disclosed

Jun 12, 2022

Last updated

Oct 20, 2026

Identifiers

CVE-2021-41749

GHSA-g7xr-v82w-qggq

References

Advisorygithub.com · CHANGELOG.md Advisorynvd.nist.gov · CVE 2021 41749 Fixgithub.com · 3fee7d50147cdf3f999cfc1e04cbc3fb3d9f2f7d Packagegithub.com · craft seomatic

Related vulnerabilities

Also affects nystudio107/craft-seomatic

This CVE is critical severity; 1 of 5 other CVEs affecting nystudio107/craft-seomatic is rated as high or higher (top: critical).

CVE-2021-41750CVE-2020-12790CVE-2020-9757CVE-2018-14716CVE-2021-44618

Same weakness: CWE-94

This CVE is critical severity, in line with the other 3 CVEs with CWE-94.

CVE-2026-63469CVE-2026-63470CVE-2026-63471Browse all CWE-94

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedOct 20, 2026

CVE-2021-41749 — craft-seomatic

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

How to detect CVE-2021-41749

Frequently Asked Questions

Is CVE-2021-41749 in your dependencies?