CVE-2026-106505: Backstage Bypass Of MkDocs Configuration Sanitizer Vulnerability

HIGH
Advisory Identifier: GHSA-p75x-jh7p-ppcx
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CVSS 7.7
CWE-426 CWE-436
Published
Advisory Summary

CVE-2026-106505 is a HIGH (CVSS 7.7) bypass of mkdocs configuration sanitizer vulnerability (CWE-426: Untrusted Search Path) affecting Backstage libraries in the npm ecosystem. The issue involves bypass of mkdocs configuration sanitizer in techdocs backend. Remediation is available by upgrading affected packages to version 1.15.4.

CVE-2026-106505 at a Glance

CVE Identifier CVE-2026-106505
GHSA Identifier GHSA-p75x-jh7p-ppcx
Severity HIGH
CVSS v3.1 Base Score 7.7
CWE Classification CWE-426: Untrusted Search Path
Affected Product Backstage
Package Ecosystem npm
Published Date
Last Updated

Security Impact

CVSS: 7.7

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity High (AC:H)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Changed (S:C)
Confidentiality High (C:H)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-106505

To remediate this vulnerability, upgrade all affected Backstage dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

@backstage/plugin-techdocs-node fixed: 1.15.4 
npm install @backstage/plugin-techdocs-node@1.15.4
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

npm ls @backstage/plugin-techdocs-node

How to Check if You Are Affected

To determine whether your Node.js application is affected by CVE-2026-106505, inspect your project dependencies using npm:

npm ls @backstage/plugin-techdocs-node

Analyze the terminal output to locate any version of Backstage in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 1.15.4), your application is affected.

Note: The npm ls @backstage/plugin-techdocs-node command inspects dependencies declared in your package.json and lockfile; it does not perform automated runtime dynamic scanning.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-426: Untrusted Search Path, where the product searches for critical resources using an externally-supplied search path that can point to resources that are not under the product's direct control. In Backstage, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Impact Users with the ability to commit changes to a repository that uses TechDocs can circumvent the MkDocs configuration file sanitizer introduced in response to CVE-2026-25153 and execute arbitrary code on the TechDocs backend host during documentation generation. ### Patches Patched in`@backstage/plugin-techdocs-node` version `1.15.4` ### Workarounds If you cannot upgrade immediately: - Use Docker mode with restricted access: Configure TechDocs with `runIn: docker` instead of `runIn: local`. This provides container isolation, though it does not fully mitigate the risk. - Limit repository write access to trusted parties, since exploitation requires the ability to commit files to a repository with TechDocs enabled. - Review incoming changes to MkDocs configuration files as part of your code review process.

CVE-2026-106505 Affected Backstage Versions

1 component(s)
Fixed Versions:
1.15.4
Product / Package Ecosystem Affected Versions Fixed Version
@backstage/plugin-techdocs-node
npm/@backstage/plugin-techdocs-node
npm
< 1.15.4
1.15.4

References

GitHub Advisory / Wiki ADVISORY
https://github.com/backstage/backstage/security/advisories/GHSA-p75x-jh7p-ppcx
NVD — CVE-2026-106505 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-106505
Security Fix Commit FIX COMMIT
https://github.com/backstage/backstage/commit/a7d995f11a5d27f0efbdbe8bb6c21b06988c79c9
Security Fix Commit FIX COMMIT
https://github.com/backstage/backstage/commit/ef92d3d2b76046205c580e7152956514c15640db
Backstage Source Repository REPOSITORY
https://github.com/backstage/backstage
Backstage Release RELEASE
https://github.com/backstage/backstage/releases/tag/v1.50.5
Backstage Release RELEASE
https://github.com/backstage/backstage/releases/tag/v1.54.6

Frequently Asked Questions

What is CVE-2026-106505?
CVE-2026-106505 is a security vulnerability in Backstage involving Bypass of MkDocs configuration sanitizer in TechDocs backend under CWE-426: Untrusted Search Path.
Which Backstage versions are affected?
Affected versions include releases prior to 1.15.4 across affected packages: @backstage/plugin-techdocs-node.
What version fixes CVE-2026-106505?
Upgrading to 1.15.4 (or the latest patched release for your respective branch) resolves the vulnerability.
Is @backstage/plugin-techdocs-node affected?
Yes, @backstage/plugin-techdocs-node is affected in releases prior to 1.15.4. Upgrade your dependency to 1.15.4 or later.
What is the CVSS score of CVE-2026-106505?
CVE-2026-106505 has a CVSS v3.1 base score of 7.7 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:L.
What CWE is associated with CVE-2026-106505?
CVE-2026-106505 is classified under CWE-426: Untrusted Search Path (The product searches for critical resources using an externally-supplied search path that can point to resources that are not under the product's direct control.).
How can I check npm dependencies for CVE-2026-106505?
Run the dependency tree command: 'npm ls @backstage/plugin-techdocs-node'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-p75x-jh7p-ppcx",
  "modified" : "2026-10-07T16:23:52Z",
  "published" : "2026-10-07T16:23:52Z",
  "aliases" : [ "CVE-2026-106505" ],
  "summary" : "Backstage: Bypass of MkDocs configuration sanitizer in TechDocs backend",
  "details" : "### Impact\n\nUsers with the ability to commit changes to a repository that uses TechDocs can circumvent the MkDocs configuration file sanitizer introduced in response to CVE-2026-25153 and execute arbitrary code on the TechDocs backend host during documentation generation.\n\n### Patches\n\nPatched in`@backstage/plugin-techdocs-node` version `1.15.4`\n\n### Workarounds\n\nIf you cannot upgrade immediately:\n\n- Use Docker mode with restricted access: Configure TechDocs with `runIn: docker` instead of `runIn: local`. This provides container isolation, though it does not fully mitigate the risk.\n- Limit repository write access to trusted parties, since exploitation requires the ability to commit files to a repository with TechDocs enabled.\n- Review incoming changes to MkDocs configuration files as part of your code review process.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "npm",
      "name" : "@backstage/plugin-techdocs-node"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.15.4"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/security/advisories/GHSA-p75x-jh7p-ppcx"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-106505"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/commit/a7d995f11a5d27f0efbdbe8bb6c21b06988c79c9"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/commit/ef92d3d2b76046205c580e7152956514c15640db"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/backstage/backstage"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/releases/tag/v1.50.5"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/backstage/backstage/releases/tag/v1.54.6"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-426", "CWE-436" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-10-07T16:23:52Z",
    "nvd_published_at" : "2026-10-06T22:17:05Z"
  }
}