CVE-2026-40964: Cloud Foundry Authentication Bypass Exposes All Logs and Metrics

Technical summary

CVE-2026-40964 is an authentication bypass vulnerability in cf-auth-proxy stemming from improper JWT validation (CWE-287). The flaw permits unauthenticated remote actors to mint tokens that cf-auth-proxy accepts as valid logs.admin credentials. The root cause involves the proxy's failure to properly validate JWT signatures or claims before granting access to the log-cache API endpoints. No integrity or availability impact is indicated; the exposure is limited to confidentiality of logs and metrics across all Cloud Foundry applications and platform components. CVSS v3.1 score of 7.5 (HIGH) reflects high confidentiality impact via a network-accessible, authentication-less vector.

Business impact

Any organization running affected Cloud Foundry instances faces immediate exposure of sensitive application and infrastructure logs containing customer data, credentials, API keys, database connection strings, and proprietary business logic. An attacker can enumerate all deployed applications, extract detailed operational insights, and plan further attacks with minimal effort. For multi-tenant or hosted platforms, this constitutes a severe data breach vector affecting all tenants simultaneously. The read-only scope limits immediate damage to confidentiality, but logs often contain security findings and system weaknesses useful for follow-on exploitation.

Affected systems

Log-cache_release versions up to and including v3.2.6 are vulnerable. Cloud Foundry Deployment installations up to v55.?.0 (inclusive) that bundle vulnerable log-cache_release versions are affected. Verify your deployment version and bundled log-cache_release version against your manifest or deployment history. Any Cloud Foundry instance exposing cf-auth-proxy to untrusted networks should be considered at risk unless already patched.

Exploitability

Exploitability is high. The attack requires only network connectivity to cf-auth-proxy—no credentials, no user interaction, no special tooling beyond standard JWT libraries. An attacker can craft a forged JWT token with logs.admin claims in seconds and retrieve all logs and metrics. Proof of impact is trivial: make an authenticated request to the Loggregator API and receive application logs. This is not a theoretical vulnerability; it is straightforward to exploit at scale.

Remediation

Upgrade log-cache_release to v3.2.7 or later immediately. For Cloud Foundry Deployment, upgrade to v55.?.0 or later (or verify that your current version bundles log-cache_release v3.2.7 or newer). Coordinate with your Cloud Foundry operations team to test and stage the patch in a non-production environment before production rollout. No workarounds or configuration changes mitigate the underlying flaw; patching is mandatory.

Patch guidance

Update log-cache_release to v3.2.7 or later as the primary remediation. Cloud Foundry Deployment operators should upgrade to v55.?.0 or later, which includes the patched log-cache_release. Verify the bundled log-cache_release version in release notes before deployment. Test patches in staging environments to confirm no operational impact. Rolling restarts of cf-auth-proxy and log-cache components are typically required; schedule downtime if necessary. Monitor logs during and after deployment for any authentication or API errors.

Detection guidance

Monitor cf-auth-proxy access logs for requests with anomalous or forged JWT tokens—look for requests from unexpected sources or tokens with suspicious claims. Check for repeated API calls to log-cache endpoints (e.g., /api/v1/read) originating from external IPs. Review logs for access to logs.admin scope by users or service accounts that should not have that privilege. Implement JWT signature validation and claims auditing if not already in place. Analyze historical logs for signs of prior unauthorized access if the vulnerability existed for an extended period. Network segmentation limiting cf-auth-proxy exposure to internal sources only reduces risk until patching completes.

Why prioritize this

This vulnerability merits immediate patching because it is unauthenticated, remotely exploitable, requires no user interaction, and exposes all application and platform logs across an entire Cloud Foundry deployment. The HIGH CVSS score and straightforward attack vector combined with the breadth of data exposed (every app, every metric) make it a top-priority remediation. Organizations in regulated industries face compliance violations if logs containing sensitive data are breached via this flaw.

Risk score, explained

CVSS v3.1 score of 7.5 (HIGH) reflects AV:N/AC:L/PR:N/UI:N—network-accessible, low complexity, no privileges required, no user interaction—coupled with high confidentiality impact (C:H) and no integrity or availability impact (I:N/A:N). The score appropriately weights the ease of exploitation and breadth of exposure against the read-only scope. In practice, organizations handling sensitive data should treat this as critical due to the content exposure risk, even though the technical CVSS is HIGH rather than CRITICAL.

Frequently asked questions