CVE-2026-106503: Access Control Flaw (CVSS 8.1)

Description

Backstage is an open framework for building developer portals. Prior to 3.3.1, 3.4.1, 4.0.3 and 4.1.0, the @backstage/plugin-scaffolder-backend package is affected by scaffolder action input authorization bypass. An authenticated user with access to affected Scaffolder templates could bypass configured action restrictions. Depending on integration credentials, this could grant unauthorized access to repositories and related source-control resources. This issue is fixed in versions 3.3.1, 3.4.1, 4.0.3 and 4.1.0.

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CVSS v3.1 Score

8.1

HIGH

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

EPSS — Exploit Prediction

0.0049

Probability of exploitation

0.42%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-178 CWE-178

CWE-284 CWE-284

References

Other References

https://github.com/backstage/backstage/commit/11c1384c0649b8ab26391c6a4e4f34b80ab0d188 https://github.com/backstage/backstage/commit/a91ed72d540e80b62a73b39bb1563ff5018d52d1 https://github.com/backstage/backstage/commit/e307e4f487103d815e484291b3fda778ab9983bf https://github.com/backstage/backstage/releases/tag/v1.49.6 https://github.com/backstage/backstage/releases/tag/v1.50.5 https://github.com/backstage/backstage/releases/tag/v1.54.6 https://github.com/backstage/backstage/security/advisories/GHSA-hmp2-4m7g-22cv

Frequently Asked Questions

What is CVE-2026-106503? +

Backstage is an open framework for building developer portals. Prior to 3.3.1, 3.4.1, 4.0.3 and 4.1.0, the @backstage/plugin-scaffolder-backend package is affected by scaffolder action input authorization bypass. An authenticated user with access to affected Scaffolder templates could bypass configured action restrictions. Depending on integration credentials, this could grant unauthorized access to repositories and related source-control resources. This issue is fixed in versions 3.3.1, 3.4.1, 4.0.3 and 4.1.0. It has a CVSS v3.1 base score of 8.1 (HIGH).

How severe is CVE-2026-106503? +

CVE-2026-106503 has a CVSS v3.1 score of 8.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0049, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-106503? +

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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