CVE-2026-34750: Payload insufficient filename validation in client-upload signed-URL endpoints

CVE-2026-34750 · Severity: medium · CVSS 6.5 · Published 2026-04-01

Payload CMS allows users to upload files to cloud storage (AWS S3, Google Cloud Storage, Azure, or Cloudflare R2) using signed URLs. The file upload endpoints do not properly validate filenames, allowing an attacker to craft malicious filenames that escape the intended storage directory and write files to unauthorized locations. This could allow a logged-in attacker to overwrite or place files outside their intended upload area, potentially compromising data integrity or enabling further attacks.

Technologies: PayloadCMS Payload. Vendors: npm, PayloadCMS.

Quick answers

Is CVE-2026-34750 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-34750 being exploited in the wild.
How severe is CVE-2026-34750?
Medium severity, with a CVSS score of 6.5, published 1 April 2026.
Which products and versions are affected?
@payloadcms/storage-azure (npm) SEMVER:introduced=0,fixed=3.78.0; @payloadcms/storage-gcs (npm) SEMVER:introduced=0,fixed=3.78.0; @payloadcms/storage-r2 (npm) SEMVER:introduced=0,fixed=3.78.0; @payloadcms/storage-s3 (npm) SEMVER:introduced=0,fixed=3.78.0.
Is there a fix for CVE-2026-34750?
Yes. @payloadcms/storage-azure (npm): upgrade to 3.78.0 or later; @payloadcms/storage-gcs (npm): upgrade to 3.78.0 or later; @payloadcms/storage-r2 (npm): upgrade to 3.78.0 or later; @payloadcms/storage-s3 (npm): upgrade to 3.78.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-34750 attacked?
It is attacked over the network.
Am I affected by CVE-2026-34750?
Check whether you run @payloadcms/storage-azure (npm), @payloadcms/storage-gcs (npm), @payloadcms/storage-r2 (npm) or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • @payloadcms/storage-azure (npm): upgrade to 3.78.0 or later
    npm install @payloadcms/storage-azure@3.78.0
  • @payloadcms/storage-gcs (npm): upgrade to 3.78.0 or later
    npm install @payloadcms/storage-gcs@3.78.0
  • @payloadcms/storage-r2 (npm): upgrade to 3.78.0 or later
    npm install @payloadcms/storage-r2@3.78.0
  • @payloadcms/storage-s3 (npm): upgrade to 3.78.0 or later
    npm install @payloadcms/storage-s3@3.78.0

Technical details

The vulnerability is a path traversal flaw (CWE-22) in the client-upload signed-URL endpoints for S3, GCS, Azure, and R2 storage adapters. The root cause is insufficient filename sanitization that fails to prevent directory traversal sequences in filenames. An attacker with network access to these endpoints and valid user credentials (low privilege) can supply crafted filenames containing path traversal characters to escape the intended storage bucket/directory. Successful exploitation allows modification of file integrity by writing files to unintended locations. The vulnerability affects all versions before v3.78.0, which hardened filename validation. A patch is available; as a temporary workaround, access to these endpoints should be restricted to trusted users.

Affected products

  • Payload @payloadcms/storage-s3 < 3.78.0
  • Payload @payloadcms/storage-gcs < 3.78.0
  • Payload @payloadcms/storage-azure < 3.78.0
  • Payload @payloadcms/storage-r2 < 3.78.0

Identifiers

  • CVE-2026-34750
  • GHSA-frq9-7j6g-v74x

Timeline

  • 2026-04-01: disclosed: Vulnerability published via GitHub Security Advisory
  • 2026-04-01: patched: Fix released in v3.78.0

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.