How severe is CVE-2025-66305?

No CVSS score has been assigned to CVE-2025-66305 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-66305?

CVE-2025-66305 affects the following packages: getgrav/grav (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2025-66305?

Update getgrav/grav to 1.8.0-beta.27 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66305 is resolved across your whole dependency graph.

How do I detect CVE-2025-66305 in my Packagist dependencies?

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

How do I mitigate CVE-2025-66305 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.

How does O3 Security protect against CVE-2025-66305?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-66305 can be triaged on real exposure rather than presence alone.

Is CVE-2025-66305 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-66305 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-2025-66305?

CVE-2025-66305 has an EPSS (Exploit Prediction Scoring System) score of 0.4%, placing it in the 33th 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-2025-66305?

CVE-2025-66305 is classified as CWE-248 (CWE-248). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2025-66305 published, and has it been updated?

CVE-2025-66305 was published on December 1, 2025 and was last updated on August 12, 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-2025-66305 — getgrav/grav

Fix: getgrav/grav@ed640a1

CVE-2025-66305 is a CWE-248 vulnerability in getgrav/grav. A fix is available for getgrav/grav — see the affected versions and patch details below.

Grav vulnerable to Denial of Service via Improper Input Handling in 'Supported' Parameter

Also known asGHSA-m8vh-v6r6-w7p6

Published

Dec 1, 2025

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 19, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-66305.

EPSS Exploitation Probability

via FIRST.org ↗

0.4%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs33th percentile — riskier than 33% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

1 pkg affected

🐘getgrav/grav

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

Endpoint: admin/config/system
Submenu: Languages
Parameter: Supported
Application: Grav v 1.7.48

Summary

A Denial of Service (DoS) vulnerability was identified in the "Languages" submenu of the Grav admin configuration panel (/admin/config/system). Specifically, the Supported parameter fails to properly validate user input. If a malformed value is inserted—such as a single forward slash (/) or an XSS test string—it causes a fatal regular expression parsing error on the server.

This leads to application-wide failure due to the use of the preg_match() function with an improperly constructed regular expression, resulting in the following error:

preg_match(): Unknown modifier 'o' File: /system/src/Grav/Common/Language/Language.php line 244

Once triggered, the site becomes completely unavailable to all users.

Details

Vulnerable Endpoint: POST /admin/config/system
Submenu: Languages
Parameter: Supported

The application dynamically constructs a regular expression using the contents of the Supported field without escaping the input using preg_quote() or proper validation. This allows attackers to inject invalid syntax into the regex engine, crashing the application during language resolution.

Stack trace excerpt:

Whoops \ Exception \ ErrorException (E_WARNING) preg_match(): Unknown modifier 'o' /system/src/Grav/Common/Language/Language.php244

Proof of Concept (PoC)

Payloads:

/

Steps to Reproduce:

Log into the Grav Admin Panel.
Navigate to: Configuration → System → Languages.
Locate the Supported field.
Insert one of the payloads above (e.g., a single slash /).
Click Save.

Observe: All pages in the application begin throwing a fatal error and become inaccessible.

Impact

Application-wide Denial of Service (DoS)
All login and admin views crash with the same error
Potentially exploitable by:
- Admin panel users
- CSRF if misconfigured

References

CWE-1333: Improper Regular Expression
CWE-20: Improper Input Validation

Discoverer

Marcelo Queiroz

by CVE-Hunters

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`getgrav/grav`	all versions	1.8.0-beta.27`composer require getgrav/grav:^1.8.0-beta.27`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for getgrav/grav, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update getgrav/grav to 1.8.0-beta.27 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66305 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-66305 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2025-66305. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

**Endpoint**: `admin/config/system` **Submenu**: `Languages` **Parameter**: `Supported` **Application**: Grav v 1.7.48 --- ## Summary A Denial of Service (DoS) vulnerability was identified in the **"Languages"** submenu of the Grav **admin configuration panel** (`/admin/config/system`). Specifically, the `Supported` parameter fails to properly validate user input. If a malformed value is inserted—such as a single forward slash (`/`) or an XSS test string—it causes a fatal regular expression parsing error on the server. This leads to application-wide failure due to the use of the `pre

O3 Security · Impact-Aware SCA

Is CVE-2025-66305 in your dependencies?

O3 Security finds CVE-2025-66305 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

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