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Sliver C2 WireGuard netstack unrestricted client-to-client access
CVE-2025-27093 affects the Sliver command-and-control framework’s custom WireGuard netstack in versions 1.5.43 and earlier, as well as the 1.6.0-dev development version. The vulnerable netstack does not enforce traffic restrictions between WireGuard clients, allowing peers on the Sliver WireGuard network to communicate with each other without intended isolation. As a result, compromised or additional WireGuard clients can reach services exposed by other clients, including operator-host services bound to the WireGuard interface, and can access port forwards that were expected to be limited. The issue is effectively a missing authorization/network-segmentation control within the WireGuard client mesh, rather than a memory corruption flaw.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation allows unrestricted lateral network access between Sliver WireGuard clients. This can expose operator systems and other connected clients to scanning, direct connection attempts, and exploitation of services such as RDP, SSH, or SMB if those services are reachable via the WireGuard interface. The advisory notes potential information disclosure and remote code execution on operator machines depending on what services are exposed. In addition, leaked or recovered beacon WireGuard keypairs can be reused to instantiate rogue clients, maintain persistence within the WireGuard network, and access port-forwarded services from other implants.
If you can’t patch tonight, do this now.
If immediate upgrade is not possible, enforce a default-deny posture between WireGuard clients and permit only explicitly required flows. Apply host-based firewall rules on operator systems to block or tightly restrict inbound access on the WireGuard interface, especially for management services such as RDP, SSH, and SMB. Avoid binding sensitive services to 0.0.0.0 when that makes them reachable through the WireGuard interface. Limit or disable WireGuard-based port forwarding where feasible. Reduce the risk of key reuse by protecting beacon processes from memory or process dumping and restricting access to systems from which WireGuard private keys could be recovered.
Patch, then assume compromise.
Upgrade Sliver to version 1.5.44 or later, which fixes the netstack behavior. All deployments using Sliver WireGuard functionality should be updated. After upgrading, review WireGuard peer isolation assumptions, validate that client-to-client traffic is appropriately restricted, and reassess operator host firewall policy and service bindings to ensure sensitive services are not unnecessarily exposed over the WireGuard interface.
No public exploits tracked yet. Mallory keeps watching.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.