CVE-2026-12539 Docker Sandboxes ICMP egress restriction bypass after daemon restart
Attackers in Docker Sandboxes can bypass ICMP egress restrictions after daemon restarts to perform reconnaissance and exfiltrate data via ICMP covert channels.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-12539?
CVE-2026-12539 is a medium-severity vulnerability in Docker Sandboxes, published on 18 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-12539?
How do I fix CVE-2026-12539?
No fix has been published for CVE-2026-12539 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-12539 being exploited?
There is no known exploitation of CVE-2026-12539 in the wild and no public exploit code.
Sources
Also known as GHSA-x6hr-f96v-hhgg.