Incus OVN TLS verification accepts peer-supplied roots and permits endpoint impersonation
Key facts
- Attack vector
- Adjacent network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- High
- Attack requirements
- None
- Impact type
- Spoofing, Security bypass
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA and GitHub. Impact type from CWE-295 and CWE-287.
Summary
Incus is a system container and virtual machine manager. In versions before 7.0.0, broken TLS validation logic in the OVN database connection logic can allow connections to an attacker's OVN database. The OVN client implementations disable Go standard TLS server verification and replace it with custom peer-certificate verification logic. That replacement verifier does not anchor trust in the configured CA certificate. Instead, it constructs the verification root set from certificates supplied by the peer during the handshake, so the configured CA is parsed but not used as the trust anchor for the final verification decision. In OVN-enabled deployments that use these SSL database connection paths, an attacker able to impersonate or intercept the OVN endpoint on the management network can present a rogue self-signed certificate chain, and Incus will accept this certificate as valid. This issue defeats the intended CA-based trust model for OVN database connections and permits endpoint impersonation by an active attacker in a suitable network position. This issue is fixed in version 7.0.0.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| lxc | incus | before 7.0.0 | 7.0.0 | Patch available | CNA |
| — | github.com/lxc/incus/v6/cmd/incusd (Go) | before 7.0.0 | 7.0.0 | Patch available | GHSA-c839-4qxr-j4x3 |
- incus Vendorlxc Affected before 7.0.0 Fixed in 7.0.0 Patch available CNA
- github.com/lxc/incus/v6/cmd/incusd (Go) Vendor— Affected before 7.0.0 Fixed in 7.0.0 Patch available GHSA-c839-4qxr-j4x3
Remediation
- Fix · CNA incus (lxc) Fixed in 7.0.0
- Fix · GHSA-c839-4qxr-j4x3 github.com/lxc/incus/v6/cmd/incusd (Go) Fixed in 7.0.0 Advisory →
Vendor assessments
Timeline
- 2026-10-02 Threatist record created from CVE-2026-40243
- 2026-10-03 Alias added: GHSA-c839-4qxr-j4x3
References
Other 5
- https://github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_icnb.go
- https://github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_icsb.go
- https://github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_nb.go
- https://github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_sb.go
- https://github.com/lxc/incus
More lxc Incus vulnerabilities
- TI-2026-19296 Incus container image templating arbitrary host file read and write CVSS 3.1HIGH 8.7
- TI-2026-19295 Incus container environment configuration newline injection CVSS 3.1HIGH 8.7
- TI-2025-39899 Incus vulnerable to local privilege escalation through custom storage volumes CVSS 4.0HIGH 8.6
- TI-2026-29045 Incus out-of-bounds panic in snapshot metadata handling allows denial of service CVSS 4.0HIGH 7.1
- TI-2026-29009 Incus nil-pointer dereference in storage bucket import allows denial of service CVSS 4.0HIGH 7.1
- TI-2026-26122 Incus vulnerable to denial of source through crafted bucket backup file CVSS 3.1MEDIUM 6.5
Sources
- CVE-2026-40243 · CVE Program
- CVE-2026-40243 · NVD
- FIRST EPSS
- GHSA-c839-4qxr-j4x3 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-40243 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences