Astro: Authorization Bypass via Decode Iteration Limit and Rewrite Path Canonicalization Mismatch

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

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

EPSS

• CVE-2026-59731: 0.33% estimated exploitation activity in the next 30 days; percentile 26.41 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Astro 6.4.7 Authorization Bypass via Decode Iteration Limit and Rewrite Path Canonicalization Mismatch Summary Astro 6.4.7 appears to reintroduce a middleware authorization bypass pattern when a request path is encoded more deeply than the newly introduced iterative URL decoder's maximum decoding depth. The issue occurs because Astro performs authorization decisions on a partially decoded pathname after reaching a decoding iteration cap, while later route matching logic performs an additional decodeURI() operation and resolves the request to a protected route. As a result, middleware and route matching may operate on different pathname representations, enabling authorization bypasses under specific application patterns. Potential CWE: CWE-647 – Use of Non-Canonical URL Paths for Authorization Decisions --- Vulnerable Pattern Middleware authorization sees: Later rewrite route matching sees: This discrepancy allows a request that bypasses middleware checks to subsequently resolve to a…

Published by the source

20 Jul 2026, 21:58 UTC

Last modified by the source

20 Jul 2026, 22:00 UTC

Source last checked

26 Oct 2026, 12:57 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-vj59-8hwv-xxmv

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-vj59-8hwv-xxmv

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# Patch Next advisory brief: CVE-2026-59731

Advisory: Astro: Authorization Bypass via Decode Iteration Limit and Rewrite Path Canonicalization Mismatch
IDs: CVE-2026-59731, GHSA-vj59-8hwv-xxmv
Record: https://patchnext.com/advisories/cve-2026-59731 (revision 2, source checked 26 Oct 2026, 12:57 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.2)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: astro 6.4.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm astro: affected >= 6.4.7, < 6.4.8; fixed in 6.4.8

## 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://osv.dev/vulnerability/GHSA-vj59-8hwv-xxmv (OSV record GHSA-vj59-8hwv-xxmv lists affected ranges: npm astro >=6.4.7 <6.4.8 (fixed))
- Verified: https://github.com/advisories/GHSA-vj59-8hwv-xxmv (GitHub-reviewed advisory GHSA-vj59-8hwv-xxmv lists affected ranges: npm astro >=6.4.7 <6.4.8)

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