CVE-2026-105867 payloadcms CVE debrief

Who should care

Defenders responsible for Payload installations with client uploads enabled for multiple collections sharing an S3 bucket should assess exposure and prioritize upgrading to >= 3.90.0 or >= 4.0.0-canary.34.

Why it matters

CVE-2026-105867 allows an authenticated user to overwrite S3 objects belonging to another upload collection, bypassing access controls and prior file validation. Defenders should prioritize upgrading Payload packages to >= 3.90.0 or >= 4.0.0-canary.34 to prevent potential overwriting of S3 objects.

• Potential overwriting of S3 objects belonging to other upload collections
• Bypassing of access controls and prior file validation
• Verification of affected versions and configurations is necessary
• Upgrade to >= 3.90.0 or >= 4.0.0-canary.34 is required to prevent potential overwriting

Technical summary

An authenticated user could overwrite an existing S3 object belonging to another upload collection, bypassing that collection's access controls and prior file validation. This occurs when client uploads are enabled for multiple collections that share an S3 bucket and useCompositePrefixes is not configured or is set to false. The vulnerability allows potential overwriting of S3 objects belonging to other upload collections, bypassing access controls and prior file validation. Upgrade to >= 3.90.0 or >= 4.0.0-canary.34 is required to prevent potential overwriting of S3 objects.

Defensive priority

Defenders should prioritize upgrading Payload packages to >= 3.90.0 or >= 4.0.0-canary.34 to prevent potential overwriting of S3 objects.

Recommended defensive actions

• Upgrade Payload packages to >= 3.90.0 or >= 4.0.0-canary.34
• Disable client uploads until upgrade is possible
• Verify affected versions and configurations
• Monitor for potential overwriting of S3 objects
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The source corpus provides details on the vulnerability, including the impact, patches, and workarounds. However, it does not provide information on exploitation or victims. The CVE allows an authenticated user to overwrite S3 objects belonging to another upload collection, bypassing access controls and prior file validation. Client uploads are enabled for multiple collections that share an S3 bucket and useCompositePrefixes is not configured or is set to false.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.