How severe is CVE-2026-28783?

No CVSS score has been assigned to CVE-2026-28783 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-28783?

CVE-2026-28783 affects the following packages: craftcms/cms (Packagist), craftcms/cms (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2026-28783?

Update craftcms/cms to 5.9.0-beta.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-28783 is resolved across your whole dependency graph.

How do I detect CVE-2026-28783 in my Packagist dependencies?

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

How do I mitigate CVE-2026-28783 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-2026-28783 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-28783 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-2026-28783?

CVE-2026-28783 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 44th 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-2026-28783?

CVE-2026-28783 is classified as Code Injection (CWE-94), CWE-184 (CWE-184), CWE-1336 (CWE-1336). These weakness types 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-2026-28783 published, and has it been updated?

CVE-2026-28783 was published on March 4, 2026 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

CVE-2026-28783 — cms

Fix: craftcms/cms#18208

CVE-2026-28783 is a Code Injection vulnerability in craftcms/cms. A fix is available for craftcms/cms — see the affected versions and patch details below.

Craft has a Twig Function Blocklist Bypass

Also known asGHSA-5fvc-7894-ghp4

Published

Mar 4, 2026

Updated

Oct 24, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 31, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-28783.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs44th percentile — riskier than 44% of all scored CVEsHighest risk

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

Real-World Exposure

2 pkgs affected

🐘craftcms/cms🐘craftcms/cms

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

Craft CMS implements a blocklist to prevent potentially dangerous PHP functions from being called via Twig non-Closure arrow functions.

In order to be able to successfully execute this attack, you need to either have allowAdminChanges enabled on production, or a compromised admin account, or an account with access to the System Messages utility.

Several PHP functions are not included in the blocklist, which could allow malicious actors with the required permissions to execute various types of payloads, including RCEs, arbitrary file reads, SSRFs, and SSTIs.

Twig has already deprecated this behavior, and it will eventually be removed from Twig altogether.

https://github.com/twigphp/Twig/blob/946ddeafa3c9f4ce279d1f34051af041db0e16f2/src/Extension/CoreExtension.php#L2096

This has been resolved in Craft 4.17.0 and 5.9.0, which removes the blocklist and disables all non-Clousure arrow functions in Twig globally via the enableTwigSandbox config setting. That setting is enabled by default on all new Craft projects. Existing Craft projects will need to enable the config setting to take advantage of it.

Existing projects should update to the patched versions of 5.9.0 and 4.17.0 to mitigate the issue and enable the config setting.

Resources

https://github.com/craftcms/cms/pull/18208

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`craftcms/cms`	≥ 5.0.0-RC1&&< 5.9.0-beta.1	5.9.0-beta.1`composer require craftcms/cms:^5.9.0-beta.1`
🐘Packagist	`craftcms/cms`	≥ 4.0.0-RC1&&< 4.17.0-beta.1	4.17.0-beta.1`composer require craftcms/cms:^4.17.0-beta.1`

Affected Products

1 product · 8 configurations

Application

craft cmscraftcms

> 5.0.0 && < 5.9.0

2 versions

4.0.05.0.0

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for craftcms/cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update craftcms/cms to 5.9.0-beta.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-28783 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.

Frequently Asked Questions

Craft CMS implements a blocklist to prevent potentially dangerous PHP functions from being called via Twig non-Closure arrow functions. In order to be able to successfully execute this attack, you need to either have `allowAdminChanges` enabled on production, or a compromised admin account, or an account with access to the System Messages utility. Several PHP functions are not included in the blocklist, which could allow malicious actors with the required permissions to execute various types of payloads, including RCEs, arbitrary file reads, SSRFs, and SSTIs. Twig has already deprecated thi

O3 Security · Impact-Aware SCA

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