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Fencer Intel
high 8.8

CVE-2026-88064 json

Backstage: Improper input validation in TechDocs MkDocs configuration

published 2mo ago modified 28d ago also EUVD-2026-80784 , GHSA-292q-8mf5-h6g3

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository backstage/backstage. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
8.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.2%
EPSS 1.2% chance of exploitation in 30 days, percentile 68%
public exploits
0
none known

Summary

Backstage is an open framework for building developer portals. Prior to 1.14.6 and from 1.15.0 until 1.15.4, the @backstage/plugin-techdocs-node package insufficiently validates mkdocs.yml supplied by an authenticated user who can register or modify a TechDocs source. Unsafe Python YAML tags, markdown_extensions names and configuration, theme options, and extra_templates values can reach the documentation generator and cause unintended code execution. The resulting impact is limited to the files, credentials, network access, and other resources available to the TechDocs backend or build container. This issue is fixed in versions 1.14.6 and 1.15.4.

Patch / fix

  • npm @backstage/plugin-techdocs-node 1.14.6, 1.15.4
  • linuxfoundation @backstage/plugin-techdocs 1.14.6, 1.15.4
  • linuxfoundation @backstage/techdocs-common 1.14.6, 1.15.4
  • linuxfoundation auth_backend 1.14.6, 1.15.4
  • linuxfoundation backstage 1.14.6, 1.15.4
  • linuxfoundation backstage_catalog-model 1.14.6, 1.15.4
  • linuxfoundation backstage_core-components 1.14.6, 1.15.4
  • linuxfoundation backstage_plugin-catalog-backend 1.14.6, 1.15.4

Is CVE-2026-88064 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
last mo.

Exploit prediction

1.18% chance of exploitation in the next 30 days, higher than 68% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem package affected fixed in
npm @backstage/plugin-techdocs-node
<1.14.6
>=1.15.0, <1.15.4
1.14.6
1.15.4

Affected products

  • backstage backstage

Classification

Weakness
  • CWE-20 Improper Input Validation
  • CWE-1336 Improper Neutralization of Special Elements Used in a Template Engine

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of backstage/backstage published their own advisory on GitHub. Reviewed sources take precedence over it.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.