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

  • Ujawniono: 02.12.2025
  • Aktualizacja: 11.10.2026 10:22

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:

  1. Log into the Grav Admin Panel.

  2. Navigate to: Configuration → System → Languages.

  3. Locate the Supported field.

  4. Insert one of the payloads above (e.g., a single slash /).

  5. Click Save.

<img width="1897" height="639" alt="Pasted image 20250719183223" src="https://github.com/user-attachments/assets/d3a54a20-d30d-46c6-9015-722f80701cfb" />
  1. Observe: All pages in the application begin throwing a fatal error and become inaccessible.
<img width="1802" height="998" alt="Pasted image 20250719175229" src="https://github.com/user-attachments/assets/b16750c2-507f-4c30-a9bb-d07fa92bb777" />

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

Czego dotyczy

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PlatformaPaczkaPodatne wersjePoprawka w wersji
Paczka Composer getgrav/grav < 1.8.0-beta.27 1.8.0-beta.27

Odnośniki

Ocena CVSS -
Wektor CVSS
CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
Słabość (CWE)
CWE-248
Platforma
Composer
Paczka
getgrav/grav
Ujawniono
02.12.2025
Aktualizacja
11.10.2026 10:22

Źródła i licencje

OSV / GitHub Advisory Database - GHSA-m8vh-v6r6-w7p6 - CC BY 4.0

Historia podatności: getgrav/grav

Wszystkie opisane podatności tej paczki (Paczka Composer), od najnowszej. Widać, czy to jednorazowa wpadka, czy paczka, której trzeba pilnować.

Wszystkie (99) w archiwum
Wszystkich wpisów
99
Pierwsza → ostatnia
11.2019 09.2026
Bez poprawki
6
Wykorzystywana w atakach
0

Rozkład istotności

  • Krytyczna 7
  • Wysoka 47
  • Średnia 41
  • Niska 4

Ujawnienia w latach

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  42. Grav File Upload Path Traversal
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