CVE-2026-12539
MediumCVSS 5.7Exploitation Probability (EPSS)
Low risk1th percentile — higher than 1% of all known CVEs
Summary
The vulnerability in Docker Sandboxes (sbx) is that the ICMP egress block is applied only at network creation time and is not re-applied to networks rebuilt from disk after a Docker daemon restart. Consequently, a sandbox that survives a restart can forward ICMP to arbitrary hosts.
Risk Assessment
The risk is that an untrusted workload inside a sandbox can bypass the documented ICMP egress block, perform network reconnaissance, and exfiltrate data over an ICMP covert channel, regardless of the configured allowlist.
Recommendation
Update Docker Sandboxes to a version where ICMP block rules are re-applied after a Docker daemon restart. Until then, manually verify and re-apply the rules after each restart.
Original NVD description (English source)
Docker Sandboxes (sbx) blocks ICMP egress with an authorizer applied only at network-creation time, and does not re-apply it to networks rebuilt from disk when the Docker daemon restarts, so a restart-surviving sandbox forwards ICMP to arbitrary hosts. A workload inside a sandbox, which the threat model treats as untrusted, can therefore defeat the documented ICMP egress block to perform network reconnaissance and exfiltrate data over an ICMP covert channel, regardless of the configured allowlist.