Vulnerability in Linuxcontainers Incus
CVE-2026-40243
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.
Vulnerability class: Improper Certificate Validation
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.002 (11.4th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 11th percentile — 11.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.002 · change: +0.000
Affected products
- Linuxcontainers Incus
- Lxc Incus — versions < 7.0.0
Weakness classification (CWE)
References
- github.com/lxc/incus/security/advisories/GHSA-c839-4qxr-j4x3 (Exploit, Vendor Advisory)
- github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_icnb.go (Product)
- github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_icsb.go (Product)
- github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_nb.go (Product)
- github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_sb.go (Product)
Frequently asked questions
- What is CVE-2026-40243?
- CVE-2026-40243 is a medium-severity vulnerability in Linuxcontainers Incus, classified under Improper Certificate Validation. CVSS score: 4.8/10. Published 2026-05-06.
- How severe is CVE-2026-40243?
- Medium severity. CVSS v3 base score is 4.8 out of 10.