CVE-2026-103090 Google CVE debrief

Who should care

Defenders and administrators of Google OSS Agent Mesh (SAM) systems, particularly those using versions 0.1.0-alpha.1 through 0.1.0-alpha.8, should assess exposure and prioritize upgrading to version 0.1.0-alpha.9 or later.

Why it matters

CVE-2026-103090 is a high-severity vulnerability in Google OSS Agent Mesh (SAM) that allows unauthenticated remote attackers to retrieve signed Biscuit identity tokens, potentially leading to unauthorized access to mesh authorization policies and router configurations. Defenders should prioritize upgrading to version 0.1.0-alpha.9 or later and verify system configurations.

• An attacker can replay the disclosed Biscuit token as a bearer credential on /policies to read mesh authorization policies
• An attacker can replay the disclosed Biscuit token as a bearer credential on /routers/lease to overwrite advertised router multiaddrs
• Requires verification of system configurations and potential exposure
• Requires verification of applied patches and system updates

Technical summary

Missing Authentication for Critical Function (CWE-306) and Insufficiently Protected Credentials (CWE-522) in Google OSS Agent Mesh (SAM) versions 0.1.0-alpha.1 through 0.1.0-alpha.8 allow an unauthenticated remote attacker to retrieve an approved bootstrap-enrolled peer's signed Biscuit identity token. The vulnerability can be exploited via GET /enroll/status, and the disclosed token can be replayed on /policies and /routers/lease endpoints. Users should upgrade to version 0.1.0-alpha.9 or later for fixes including cryptographic proof of possession and rate limiting.

Defensive priority

High priority for upgrading to version 0.1.0-alpha.9 or later, verifying system configurations, and monitoring for suspicious activity.

Recommended defensive actions

• Upgrade to version 0.1.0-alpha.9 or later
• Verify system configurations and ensure cryptographic proof of possession of the enrollment private key
• Monitor for suspicious activity and implement rate limiting
• 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
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD vulnerability detail page provide information on the vulnerability, including its description, CVSS score, and affected versions. Evidence is limited to public CVE Program and NVD records. Defenders should verify system configurations, applied patches, and system updates. The vulnerability allows unauthenticated remote attackers to retrieve signed Biscuit identity tokens, which can be replayed as bearer credentials.

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.