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Medium, CVSS 5.1amended

Grav: Single invalid UTF-8 byte disables every rule in Security::detectXss(), bypassing the page-content XSS safety gate

CVE-2026-75834GHSA-q2j8-x8hf-63ch

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (getgrav/grav 2.0.14), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
5.1 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N · score source
EPSS
  • CVE-2026-75834: 0.26% estimated exploitation activity in the next 30 days; percentile 17.14 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Vulnerability Details Component: getgrav/grav core File: system/src/Grav/Common/Security.php Function: detectXss() (all six entries in the $patterns array use the PCRE u modifier), invoked from Grav\Common\Data\Validation::checkSafety() (the save-time XSS gate for any non-security.xsswhitelist account's blueprint field, including the page content field) and detectXssInEditorContent() (the render-time backstop for GHSA-2c4f-86xc-cr74) CWE: CWE-79 (Stored XSS), root-caused by CWE-20 (Improper Input Validation — fails open on malformed input) Severity: High CVSS: 8.0 — CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N Relationship to prior advisories This project's detectXss()/checkSafety() stack has been patched at least three times for the "page editor without super-admin rights stores an event handler that runs for site visitors" bug class: GHSA-9695-8fr9-hw5q / GHSA-c2q3-p4jr-c55f / GHSA-w8cg-7jcj-4vv2 (unquoted-attribute bypasses), GHSA-269c-h76q-8cxw (quoted-attribute-boundary bypass),…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 3 · amended ·

    Amended from ghsa record GHSA-q2j8-x8hf-63ch

  2. Revision 2 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 1 · created ·

    Published from osv record GHSA-q2j8-x8hf-63ch

Agent brief

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# Patch Next advisory brief: CVE-2026-75834

Advisory: Grav: Single invalid UTF-8 byte disables every rule in Security::detectXss(), bypassing the page-content XSS safety gate
IDs: CVE-2026-75834, GHSA-q2j8-x8hf-63ch
Record: https://patchnext.com/advisories/cve-2026-75834 (revision 3, source checked 26 Oct 2026, 14:53 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: getgrav/grav 2.0.14. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist getgrav/grav: affected < 2.0.14; fixed in 2.0.14

## Suggested inspection (read-only)
- Packagist getgrav/grav: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on getgrav/grav.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-q2j8-x8hf-63ch (OSV record GHSA-q2j8-x8hf-63ch lists affected ranges: Packagist getgrav/grav >=0 <2.0.14 (fixed))
- Verified: https://github.com/advisories/GHSA-q2j8-x8hf-63ch (GitHub-reviewed advisory GHSA-q2j8-x8hf-63ch lists affected ranges: Packagist getgrav/grav >=0 <2.0.14)

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