CVE-2021-43783

CVE-2021-43783 is a high-severity vulnerability in Linuxfoundation Backstage with a CVSS 3.x base score of 8.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.

Key facts

Description

@backstage/plugin-scaffolder-backend is the backend for the default Backstage software templates. In affected versions a malicious actor with write access to a registered scaffolder template is able to manipulate the template in a way that writes files to arbitrary paths on the scaffolder-backend host instance. This vulnerability can in some situation also be exploited through user input when executing a template, meaning you do not need write access to the templates. This method will not allow the attacker to control the contents of the injected file however, unless the template is also crafted in a specific way that gives control of the file contents. This vulnerability is fixed in version `0.15.14` of the `@backstage/plugin-scaffolder-backend`. This attack is mitigated by restricting access and requiring reviews when registering or modifying scaffolder templates.

Frequently asked questions

What is CVE-2021-43783?
@backstage/plugin-scaffolder-backend is the backend for the default Backstage software templates. In affected versions a malicious actor with write access to a registered scaffolder template is able to manipulate the template in a way that writes files to arbitrary paths on the scaffolder-backend host instance. This vulnerability can in some situation also be exploited through user input when executing a template, meaning you do not need write access to the templates. This method will not allow the attacker to control the contents of the injected file however, unless the template is also crafted in a specific way that gives control of the file contents. This vulnerability is fixed in version `0.15.14` of the `@backstage/plugin-scaffolder-backend`. This attack is mitigated by restricting access and requiring reviews when registering or modifying scaffolder templates.
How severe is CVE-2021-43783?
CVE-2021-43783 has a CVSS 3.x base score of 8.5, rated high severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity high, and availability low.
Is CVE-2021-43783 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (65th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-43783?
CVE-2021-43783 affects Linuxfoundation Backstage. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-43783?
Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-43783 published?
CVE-2021-43783 was published on 2021-11-29 and last updated on 2026-06-17.

References

Affected products (1)

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