GHSA-xvgh-hmx8-9xxf CVE-2026-106500
Backstage: Improper task state validation in Scaffolder backend
High
npm
- Severity
- 8.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.34%
- Chance of exploitation in the next 30 days. Higher than 27.05% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
- CWE-59 Improper Link Resolution Before File Access ('Link Following')
- Fix
4.1.0- Upgrade @backstage/plugin-scaffolder-backend to this version or later
Description
Impact
An authenticated user with permission to create and access Scaffolder tasks may, under specific timing and deployment conditions, affect files accessible to the Backstage backend. If backend application files are writable, the confidentiality, integrity, and availability of the backend may be compromised.
Patches
Patched in @backstage/plugin-scaffolder-backend version 4.1.0
Workarounds
- Restrict Scaffolder task creation and task-read permissions to trusted users through the permission policy.
- Limit who can register or modify templates and which Scaffolder actions may execute.
- Run backend application files read-only outside a dedicated, least-privilege Scaffolder working directory.
References
Affected versions
npm
| Package | Vulnerable | Fixed in |
|---|---|---|
| @backstage/plugin-scaffolder-backend | < 4.1.0 |
4.1.0 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
@backstage/plugin-scaffolder-backend npm → 4.1.0
- npm
npm install @backstage/plugin-scaffolder-backend@4.1.0- yarn
yarn add @backstage/plugin-scaffolder-backend@4.1.0- pnpm
pnpm add @backstage/plugin-scaffolder-backend@4.1.0
Severity breakdown
CVSS 3.1 8.5
CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H
- Attack vector
- Network
- Attack complexity
- High
- Privileges required
- Low
- User interaction
- None
- Scope
- Changed
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Weakness
CWE-362: Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
How to prevent it
- Architecture and Design: In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
- Architecture and Design: Use thread-safe capabilities such as the data access abstraction in Spring.
- Architecture and Design: Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).
- Implementation: When using multithreading and operating on shared variables, only use thread-safe functions.
- Implementation: Use atomic operations on shared variables. Be wary of innocent-looking constructs such as "x++". This may appear atomic at the code layer, but it is actually non-atomic at the instruction layer, since it involves a read, followed by a computation, followed by a write.
- Implementation: Use a mutex if available, but be sure to avoid related weaknesses such as CWE-412.
- Implementation: Avoid double-checked locking (CWE-609) and other implementation errors that arise when trying to avoid the overhead of synchronization.
- Implementation: Disable interrupts or signals over critical parts of the code, but also make sure that the code does not go into a large or infinite loop.
- Implementation: Use the volatile type modifier for critical variables to avoid unexpected compiler optimization or reordering. This does not necessarily solve the synchronization problem, but it can help.
- Architecture and Design, Operation: Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations.
CWE-59: Improper Link Resolution Before File Access ('Link Following')
The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.
How to prevent it
- Architecture and Design: Follow the principle of least privilege when assigning access rights to entities in a software system. Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.
References
Advisories
Packages
Other links
- github.com/backstage/backstage/security/advisories/GHSA-xvgh-hmx8-9xxf
- github.com/backstage/backstage/commit/0d24f1b8701f3dde6cd597f81997c1ea873a43ae
- github.com/backstage/backstage/commit/56be299dd3ef6706e13e76ea2f8a9b0dd0b6413d
- github.com/backstage/backstage/commit/9e86c95a1a3ddfd54db03731cd8678aa63495175
- github.com/backstage/backstage/releases/tag/v1.49.6
- github.com/backstage/backstage/releases/tag/v1.50.5
- github.com/backstage/backstage/releases/tag/v1.54.6
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-vwp5-f99x-x3rq Backstage has improper input validation in scaffolder task list ordering | Medium | Also affects @backstage/plugin-scaffolder-backend |
| GHSA-4xvq-3m68-h444 Backstage has sensitive information exposure in scaffolder task logs | Medium | Also affects @backstage/plugin-scaffolder-backend |
| GHSA-hmp2-4m7g-22cv Backstage: Scaffolder action input authorization bypass | High | Also affects @backstage/plugin-scaffolder-backend |
| GHSA-95p4-vv4g-jxxm Backstage may expose sensitive information in Scaffolder task failure events | Medium | Also affects @backstage/plugin-scaffolder-backend |
| GHSA-g2v8-7jhw-pp8p Backstage: Sensitive information exposure in Scaffolder | Critical | Also affects @backstage/plugin-scaffolder-backend |
| GHSA-mfvq-x7vr-rgqg Backstage: Secret-derived values may be exposed in scaffolder task logs | Medium | Also affects @backstage/plugin-scaffolder-backend |
| GHSA-29gx-h2m3-xw44 Backstage's scaffolder credential handling may allow unintended GitHub authentication fallback | Medium | Also affects @backstage/plugin-scaffolder-backend |
| GHSA-7hfw-grcm-cqm6 Backstage: Incorrect authorization in scaffolder task listing | Medium | Also affects @backstage/plugin-scaffolder-backend |
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