CefSharp.Common: FolderSchemeHandlerFactory path boundary check can expose files outside the configured root folder

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N

EPSS

• CVE-2026-48796: 0.40% estimated exploitation activity in the next 30 days; percentile 33.73 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary FolderSchemeHandlerFactory was intended to restrict served files to a configured rootFolder, but its path validation used a raw string prefix check. A request could escape to a sibling directory whose full path starts with the root folder path, allowing files outside the configured root to be served. Details In affected versions, FolderSchemeHandlerFactory canonicalized rootFolder, decoded the request path, combined it with the root, and then allowed the file when: This does not enforce a directory boundary. For example, /tmp/app/www2/secret.txt starts with /tmp/app/www, but www2 is a sibling of www, not a child. The same issue applies on Windows, for example C:\app\www2\secret.txt starts with C:\app\www. The affected code was reviewed at commit b5fef3bb4bc58798c95170078c41de92cfe9066e, assembly version 147.0.100. PoC Set rootFolder to a directory named www and create a sibling directory named www2: Register FolderSchemeHandlerFactory for <temp/www, then request: The request…

Published by the source

30 Jun 2026, 18:36 UTC

Last modified by the source

30 Jun 2026, 18:36 UTC

Source last checked

26 Oct 2026, 17:04 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-85jm-cwp2-mvpv

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# Patch Next advisory brief: CVE-2026-48796

Advisory: CefSharp.Common: `FolderSchemeHandlerFactory` path boundary check can expose files outside the configured root folder
IDs: CVE-2026-48796, GHSA-85jm-cwp2-mvpv
Record: https://patchnext.com/advisories/cve-2026-48796 (revision 1, source checked 26 Oct 2026, 17:04 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: cefsharp.common 148.0.90. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet cefsharp.common: affected < 148.0.90; fixed in 148.0.90

## Suggested inspection (read-only)
- NuGet cefsharp.common: 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 cefsharp.common.
- 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://github.com/advisories/GHSA-85jm-cwp2-mvpv (GitHub-reviewed advisory GHSA-85jm-cwp2-mvpv lists affected ranges: NuGet cefsharp.common >=0 <148.0.90)

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