CVE-2026-48058 in nebula-mesh
Summary
by MITRE • 07/28/2026
nebula-mesh is a self-hosted control plane for Slack Nebula mesh virtual private network. Prior to version 0.3.2, internal/web/session.go and internal/web/oidc.go set HttpOnly and SameSite=Lax on every cookie but never Secure. A single plaintext request to the origin (operator on a LAN, mistyped URL, HTTP→HTTPS not strictly enforced, reverse proxy misconfiguration) discloses the session. This issue has been patched in version 0.3.2.
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Analysis
by VulDB Data Team • 07/28/2026
The nebula-mesh software presents a critical cookie security vulnerability that affects versions prior to 032. This flaw resides in the session management implementation within the internal/web/session.go and internal/web/oidc.go files where cookies are configured with HttpOnly and SameSite=Lax attributes but lack the Secure flag. The absence of this crucial security parameter creates a significant exposure risk in environments where plaintext HTTP traffic may be intercepted or where network boundaries are not strictly enforced. The vulnerability operates under the principle that session tokens should only be transmitted over encrypted channels to prevent interception attacks, yet the implementation fails to enforce this fundamental requirement.
The technical nature of this flaw aligns with CWE-614, which addresses the insufficient protection of sensitive data in cookies by ensuring that the Secure attribute is properly configured. When a cookie lacks the Secure flag, it becomes vulnerable to transmission over unencrypted HTTP connections, making it susceptible to man-in-the-middle attacks and session hijacking attempts. The operational impact extends beyond simple credential theft to encompass complete session compromise, as attackers can intercept these unsecured cookies during any plaintext HTTP communication. This vulnerability is particularly dangerous in environments where reverse proxy configurations may not strictly enforce HTTPS redirection or where operators might inadvertently access the system through HTTP endpoints.
The security implications of this flaw become apparent when considering real-world attack scenarios involving network traffic interception, misconfigured reverse proxies, or operator error leading to mistyped URLs that resolve to HTTP endpoints. The vulnerability can be exploited through various attack vectors including unencrypted network traffic, improper load balancer configurations, or legacy system access points that do not enforce secure communication protocols. According to ATT&CK framework category TA0006, this represents a credential access technique where adversaries obtain session tokens without authentication, while also mapping to TA0001 for privilege escalation through session manipulation.
Mitigation strategies should focus on implementing proper cookie security configuration by adding the Secure flag to all session cookies, ensuring that the application enforces HTTPS-only communication throughout the entire attack surface. Organizations should implement strict HTTP to HTTPS redirection policies, configure reverse proxies to enforce secure connections, and conduct regular security audits of network configurations to prevent plaintext requests from reaching sensitive endpoints. Additionally, implementing comprehensive network monitoring and access controls can help detect and prevent unauthorized plaintext access attempts while ensuring that all session management components properly enforce security best practices including proper cookie attribute configuration as specified in RFC 6265 and OWASP secure coding guidelines.