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Medium, CVSS 6.3amended

Astro: Authorization bypass from missing path-segment boundary check when stripping the configured base

CVE-2026-84376GHSA-376h-93r7-7g6f

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (astro 7.2.4), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

  • npm astro

    Affected
    <= 7.2.3
    Fixed in
    7.2.4

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS 4.0
6.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N · score source
EPSS
  • CVE-2026-84376: 0.71% estimated exploitation activity in the next 30 days; percentile 53.45 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Summary Astro stripped a configured base path from request pathnames using a string-prefix check that did not verify a path-segment boundary. With base: "/app", a request to /appX/admin was treated as being under the base and resolved internally to the /admin route, while middleware still observed the public pathname /appX/admin. Middleware that authorizes routes by inspecting context.url.pathname could therefore be bypassed. Impact An unauthenticated remote attacker can bypass pathname-based middleware authorization in applications that: - Configure a non-root base. - Protect base-prefixed routes in middleware using context.url.pathname. Because routing and middleware resolved different effective pathnames, a request such as /appX/admin (or other single-character extensions like /app2/admin or /app-/admin) reached the protected /admin route without passing the middleware check that guards /app/admin. Astro's authentication guide demonstrates protecting routes in middleware via…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 4 · amended ·

    Amended from ghsa record GHSA-376h-93r7-7g6f

  2. Revision 3 · amended ·

    Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

  3. Revision 2 · amended ·

    Amended from osv record GHSA-376h-93r7-7g6f

  4. Revision 1 · created ·

    Published from ghsa record GHSA-376h-93r7-7g6f

Agent brief

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# Patch Next advisory brief: CVE-2026-84376

Advisory: Astro: Authorization bypass from missing path-segment boundary check when stripping the configured base
IDs: CVE-2026-84376, GHSA-376h-93r7-7g6f
Record: https://patchnext.com/advisories/cve-2026-84376 (revision 4, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: astro 7.2.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm astro: affected <= 7.2.3; fixed in 7.2.4

## Suggested inspection (read-only)
- `npm ls astro --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on astro.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-376h-93r7-7g6f (GitHub-reviewed advisory GHSA-376h-93r7-7g6f lists affected ranges: npm astro >=0 <=7.2.3)
- Verified: https://osv.dev/vulnerability/GHSA-376h-93r7-7g6f (OSV record GHSA-376h-93r7-7g6f lists affected ranges: npm astro >=0 <7.2.4 (fixed))

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