CVE-2026-40243

/* * Conceptual PoC: Vulnerable Verification Logic * This Go snippet demonstrates the flawed logic where the trust root * is constructed from the peer's certificates instead of a configured CA. */ package main import ( "crypto/tls" "crypto/x509" ) func vulnerableVerifyPeerCertificate(rawCerts [][]byte, verifiedChains [][]*x509.Certificate) error { // VULNERABLE LOGIC: Creating a new CertPool and adding the peer's raw certs // This effectively trusts any certificate presented by the attacker. roots := x509.NewCertPool() for _, rawCert := range rawCerts { cert, err := x509.ParseCertificate(rawCert) if err != nil { return err } roots.AddCert(cert) // Adding attacker's cert as a trusted root } opts := x509.VerifyOptions{ Roots: roots, // Using the compromised pool } // Verify the chain using the attacker-supplied roots if len(verifiedChains) > 0 { _, err := verifiedChains[0][0].Verify(opts) return err } return nil } // This function would be passed to tls.Config{VerifyPeerCertificate: ...} func main() { cfg := &tls.Config{ InsecureSkipVerify: true, VerifyPeerCertificate: vulnerableVerifyPeerCertificate, } _ = cfg }

{"cve": {"id": "CVE-2026-40243", "sourceIdentifier": "[email protected]", "published": "2026-05-06T21:16:01.070", "lastModified": "2026-05-08T17:23:38.943", "vulnStatus": "Analyzed", "cveTags": [], "descriptions": [{"lang": "en", "value": "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.\n\nIn 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."}], "metrics": {"cvssMetricV40": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "4.0", "vectorString": "CVSS:4.0/AV:A/AC:H/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X", "baseScore": 2.3, "baseSeverity": "LOW", "attackVector": "ADJACENT", "attackComplexity": "HIGH", "attackRequirements": "NONE", "privilegesRequired": "NONE", "userInteraction": "NONE", "vulnConfidentialityImpact": "LOW", "vulnIntegrityImpact": "LOW", "vulnAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "subAvailabilityImpact": "NONE", "exploitMaturity": "NOT_DEFINED", "confidentialityRequirement": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "availabilityRequirement": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "Safety": "NOT_DEFINED", "Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "valueDensity": "NOT_DEFINED", "vulnerabilityResponseEffort": "NOT_DEFINED", "providerUrgency": "NOT_DEFINED"}}], "cvssMetricV31": [{"source": "[email protected]", "type": "Primary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N", "baseScore": 4.8, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "HIGH", "privilegesRequired": "NONE", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.2, "impactScore": 2.5}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-295"}]}], "configurations": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": "cpe:2.3:a:linuxcontainers:incus:*:*:*:*:*:*:*:*", "versionEndExcluding": "7.0.0", "matchCriteriaId": "CF8EBB4B-C1F0-44C5-B063-9CF8EB6E0972"}]}]}], "references": [{"url": "https://github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_icnb.go", "source": "[email protected]", "tags": ["Product"]}, {"url": "https://github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_icsb.go", "source": "[email protected]", "tags": ["Product"]}, {"url": "https://github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_nb.go", "source": "[email protected]", "tags": ["Product"]}, {"url": "https://github.com/lxc/incus/blob/v6.22.0/internal/server/network/ovn/ovn_sb.go", "source": "[email protected]", "tags": ["Product"]}, {"url": "https://github.com/lxc/incus/security/advisories/GHSA-c839-4qxr-j4x3", "source": "[email protected]", "tags": ["Exploit", "Vendor Advisory"]}, {"url": "https://github.com/lxc/incus/security/advisories/GHSA-c839-4qxr-j4x3", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "tags": ["Exploit", "Vendor Advisory"]}]}}