CyberSecBulletin
CVE-2026-33768NVD status: Analyzed

astro: Unintended Proxy or Intermediary

Published Updated By the CyberSecBulletin desk

CVE-2026-33768 is a critical-severity unintended proxy or intermediary vulnerability in astro from Withastro, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected astro versions: < 10.0.2. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.35% chance of exploitation within 30 days, which is low compared with other CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update @astrojs/vercel to 10.0.2 or a later version.
  2. Read the advisory on github.com for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Withastroastro< 10.0.2Not stated
Astro@astrojs/vercelbefore 10.0.210.0.2

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
NoneAvailability is not affected.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.16.5MediumCNA (github.com)
CVSS 3.19.1CriticalNVD

Official description

Astro is a web framework. Prior to version 10.0.2, the @astrojs/vercel serverless entrypoint reads the x-astro-path header and x_astro_path query parameter to rewrite the internal request path, with no authentication whatsoever. On deployments without Edge Middleware, this lets anyone bypass Vercel's platform-level path restrictions entirely. The override preserves the original HTTP method and body, so this isn't limited to GET. POST, PUT, DELETE all land on the rewritten path. A Firewall rule blocking /admin/* does nothing when the request comes in as POST /api/health?x_astro_path=/admin/delete-user. This issue has been patched in version 10.0.2.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Unintended Proxy or Intermediary

The product receives a request, message, or directive from an upstream component, but the product does not sufficiently preserve the original source of the request before forwarding the request to an external actor that is outside of the product's control sphere.

How developers prevent this class of flaw

  • Enforce the use of strong mutual authentication mechanism between the two parties.
  • Whenever a product is an intermediary or proxy for transactions between two other components, the proxy core should not drop the identity of the initiator of the transaction. The immutability of the identity of the initiator must be maintained and should be forwarded all the way to the target.

More Unintended Proxy or Intermediary vulnerabilities (CWE-441)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in astro

All astro vulnerabilities

Recent Unintended Proxy or Intermediary vulnerabilities

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