CVE-2026-106558: Insecure Deserialization (CVSS 8.8)

Description

Backstage is an open framework for building developer portals. Prior to 1.14.8, 1.15.6, and 2.0.1, the @backstage/plugin-techdocs-node package improperly validated mapping-style markdown_extensions configuration. An authenticated attacker who can register or influence an SCM-backed documentation source may bypass TechDocs sanitization and cause Python objects to be imported and instantiated in the generator runtime, leading to arbitrary code execution. Earlier fixes in versions 1.14.6 and 1.15.4 did not fully address the supported mapping representation of markdown_extensions. Impact is greatest when documentation generation runs with backend credentials, filesystem access, or internal network access. This issue is fixed in versions 1.14.8, 1.15.6, and 2.0.1.

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CVSS v3.1 Score

8.8

HIGH

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

Weakness Type (CWE)

CWE-502 Deserialization of Untrusted Data

References

Other References

https://github.com/backstage/backstage/commit/32723a0fe4e12ed80535fc65d5331765c55aa91b https://github.com/backstage/backstage/commit/944edb51c8524d3664b18f2d57ba101b1c93b709 https://github.com/backstage/backstage/commit/f18e9abcc6051491862b15e4fc60e69f8d52310c https://github.com/backstage/backstage/releases/tag/v1.50.7 https://github.com/backstage/backstage/releases/tag/v1.54.9 https://github.com/backstage/backstage/releases/tag/v1.55.2 https://github.com/backstage/backstage/security/advisories/GHSA-qmw3-745m-w99g

Frequently Asked Questions

What is CVE-2026-106558? +

Backstage is an open framework for building developer portals. Prior to 1.14.8, 1.15.6, and 2.0.1, the @backstage/plugin-techdocs-node package improperly validated mapping-style markdown_extensions configuration. An authenticated attacker who can register or influence an SCM-backed documentation source may bypass TechDocs sanitization and cause Python objects to be imported and instantiated in the generator runtime, leading to arbitrary code execution. Earlier fixes in versions 1.14.6 and 1.15.4 did not fully address the supported mapping representation of markdown_extensions. Impact is greatest when documentation generation runs with backend credentials, filesystem access, or internal network access. This issue is fixed in versions 1.14.8, 1.15.6, and 2.0.1. It has a CVSS v3.1 base score of 8.8 (HIGH).

How severe is CVE-2026-106558? +

CVE-2026-106558 has a CVSS v3.1 score of 8.8 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching.

How do I check if I'm vulnerable to CVE-2026-106558? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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