CVE-2026-44726: Deno's TLS retry copies stale upgrade hook, risking plaintext traffic
A flaw in Deno’s Node.js tls compatibility layer could cause a TLS client to transmit application data in plaintext after a connection retry. When `autoSelectFamily was enabled and the first address-family attempt failed, the socket reinitialization path reused a stale TLS upgrade hook that was bound to the original, failed handle.
As a result, the replacement TCP connection was never upgraded to TLS, and any data the application wrote before the secureConnect event travelled over the network unencrypted.
A network attacker positioned to cause the initial connection attempt to fail (for example, by dropping IPv6 traffic on a dual-stack host) could deterministically trigger the fallback path and observe or tamper with traffic that the application believed was TLS-protected.
Affected APIs: Applications using Deno’s node:tls or node:https surface with autoSelectFamily enabled (the default) that wrote to the socket before the secureConnect event.
References
Code Behaviors & Features
Detect and mitigate CVE-2026-44726 with GitLab Dependency Scanning
Secure your software supply chain by verifying that all open source dependencies used in your projects contain no disclosed vulnerabilities. Learn more about Dependency Scanning →