Vulnerability-Lookup

CVE-2026-48796 (GCVE-0-2026-48796)

Vulnerability from cvelistv5 – Published: 2026-08-18 21:17 – Updated: 2026-08-19 18:19

Title

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

Summary

CefSharp provides .NET bindings for the Chromium Embedded Framework for Windows Forms and Windows Presentation Foundation applications. Prior to version 148.0.90, CefSharp/SchemeHandler/FolderSchemeHandlerFactory.cs used filePath.StartsWith(rootFolder, StringComparison.OrdinalIgnoreCase) to decide whether a decoded and canonicalized request path remained inside rootFolder. That raw prefix test did not enforce a directory boundary, so a request such as ..%2fwww2/secret.txt could escape a configured www directory into a sibling www2 directory whose path shared the same string prefix. Applications that register FolderSchemeHandlerFactory for a custom scheme or an HTTP or HTTPS scheme can therefore serve local files outside the intended root when an attacker can cause the embedded browser to request the crafted URL. The issue affects both Unix-style paths such as /tmp/app/www2 and Windows paths such as C:\app\www2, and the fix appends a directory separator to the normalized root before comparison while rejecting null bytes and alternate data stream syntax. This issue is fixed in version 148.0.90.

Severity

5.3 (Medium)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-08-19 18:03 UTC

CWE

CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Assigner

GitHub_M mitre root

References

3 references

URL	Tags
https://github.com/cefsharp/CefSharp/security/adv…	x_refsource_CONFIRM
https://github.com/cefsharp/CefSharp/commit/3475c…	x_refsource_MISC
https://github.com/cefsharp/CefSharp/releases/tag…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
cefsharp	CefSharp	Affected: < 148.0.90	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-48796

Vulnerability from fkie_nvd - Published: 2026-08-18 22:16 - Updated: 2026-08-19 19:17

Severity

5.3 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/cefsharp/CefSharp/commit/3475c7ef14119f67ec3720866bb3e4b1c6c68632
	security-advisories@github.com	https://github.com/cefsharp/CefSharp/releases/tag/v148.0.90
	security-advisories@github.com	https://github.com/cefsharp/CefSharp/security/advisories/GHSA-85jm-cwp2-mvpv

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "CefSharp",
          "vendor": "cefsharp",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 148.0.90"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "cveTags": [],
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    {
      "lang": "en",
      "value": "CefSharp provides .NET bindings for the Chromium Embedded Framework for Windows Forms and Windows Presentation Foundation applications. Prior to version 148.0.90, CefSharp/SchemeHandler/FolderSchemeHandlerFactory.cs used filePath.StartsWith(rootFolder, StringComparison.OrdinalIgnoreCase) to decide whether a decoded and canonicalized request path remained inside rootFolder. That raw prefix test did not enforce a directory boundary, so a request such as ..%2fwww2/secret.txt could escape a configured www directory into a sibling www2 directory whose path shared the same string prefix. Applications that register FolderSchemeHandlerFactory for a custom scheme or an HTTP or HTTPS scheme can therefore serve local files outside the intended root when an attacker can cause the embedded browser to request the crafted URL. The issue affects both Unix-style paths such as /tmp/app/www2 and Windows paths such as C:\\app\\www2, and the fix appends a directory separator to the normalized root before comparison while rejecting null bytes and alternate data stream syntax. This issue is fixed in version 148.0.90."
    }
  ],
  "id": "CVE-2026-48796",
  "lastModified": "2026-08-19T19:17:17.417",
  "metrics": {
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        "cvssData": {
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GHSA-85JM-CWP2-MVPV

Vulnerability from github – Published: 2026-06-30 18:36 – Updated: 2026-06-30 18:36

Summary

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

Details

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:

filePath.StartsWith(rootFolder, StringComparison.OrdinalIgnoreCase)

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:

<temp>/www/index.html
<temp>/www2/secret.txt

https://folderschemehandlerfactory.test/..%2fwww2/secret.txt

The request path is URL-decoded to ../www2/secret.txt, combined with <temp>/www, and canonicalized to:

<temp>/www2/secret.txt

Because <temp>/www2/secret.txt starts with <temp>/www as a string prefix, the affected check passes and secret.txt is served from outside rootFolder.

Expected vulnerable result: HTTP 200 with the contents of <temp>/www2/secret.txt.

Expected fixed result: 404 or equivalent not-found response because the resolved file is outside rootFolder.

Impact

Applications using FolderSchemeHandlerFactory for a custom scheme or registered HTTP/HTTPS scheme may expose local files outside the intended served directory. This is most relevant when sensitive sibling directories share the root path prefix, such as www/www2, public/public_backup, or static/static-secrets.

An attacker must be able to cause the embedded browser to request URLs handled by the affected scheme registration.

Severity

5.3 (Medium)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "package": {
        "ecosystem": "NuGet",
        "name": "CefSharp.Common"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "148.0.90"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-48796"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-06-30T18:36:12Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "### Summary\n\n`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.\n\n### Details\n\nIn affected versions, `FolderSchemeHandlerFactory` canonicalized `rootFolder`, decoded the request path, combined it with the root, and then allowed the file when:\n\n```csharp\nfilePath.StartsWith(rootFolder, StringComparison.OrdinalIgnoreCase)\n```\n\nThis 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`.\n\nThe affected code was reviewed at commit `b5fef3bb4bc58798c95170078c41de92cfe9066e`, assembly version `147.0.100`.\n\n### PoC\n\nSet `rootFolder` to a directory named `www` and create a sibling directory named `www2`:\n\n```text\n\u003ctemp\u003e/www/index.html\n\u003ctemp\u003e/www2/secret.txt\n```\n\nRegister `FolderSchemeHandlerFactory` for `\u003ctemp\u003e/www`, then request:\n\n```text\nhttps://folderschemehandlerfactory.test/..%2fwww2/secret.txt\n```\n\nThe request path is URL-decoded to `../www2/secret.txt`, combined with `\u003ctemp\u003e/www`, and canonicalized to:\n\n```text\n\u003ctemp\u003e/www2/secret.txt\n```\n\nBecause `\u003ctemp\u003e/www2/secret.txt` starts with `\u003ctemp\u003e/www` as a string prefix, the affected check passes and `secret.txt` is served from outside `rootFolder`.\n\nExpected vulnerable result: HTTP 200 with the contents of `\u003ctemp\u003e/www2/secret.txt`.\n\nExpected fixed result: 404 or equivalent not-found response because the resolved file is outside `rootFolder`.\n\n### Impact\n\nApplications using `FolderSchemeHandlerFactory` for a custom scheme or registered HTTP/HTTPS scheme may expose local files outside the intended served directory. This is most relevant when sensitive sibling directories share the root path prefix, such as `www`/`www2`, `public`/`public_backup`, or `static`/`static-secrets`.\n\nAn attacker must be able to cause the embedded browser to request URLs handled by the affected scheme registration.",
  "id": "GHSA-85jm-cwp2-mvpv",
  "modified": "2026-06-30T18:36:12Z",
  "published": "2026-06-30T18:36:12Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/cefsharp/CefSharp/security/advisories/GHSA-85jm-cwp2-mvpv"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/cefsharp/CefSharp"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "CefSharp.Common: `FolderSchemeHandlerFactory` path boundary check can expose files outside the configured root folder"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.

Action not permitted

CVE-2026-48796 (GCVE-0-2026-48796)

FKIE_CVE-2026-48796

GHSA-85JM-CWP2-MVPV

Summary

Details

PoC

Impact

Tags

Sightings

Nomenclature