CVE-2026-44726 Deno: TLS retry copies stale upgrade hook, risking plaintext traffic
A network attacker can force plaintext transmission in Deno's TLS layer by triggering a connection retry, allowing them to observe or tamper with supposedly encrypted traffic.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-44726?
CVE-2026-44726 is a high-severity vulnerability in denoland deno, published on 23 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Deno is a JavaScript, TypeScript, and WebAssembly runtime. From 2.0.0 until 2.7.8, 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. This vulnerability is fixed in 2.7.8.
Weakness: CWE-319
Which versions are affected by CVE-2026-44726?
2 open source packages ship an affected version, including deno. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
deno crates.io | From 2.0.0 | 2.7.8 |
deno crates.io | From 2.0.0 | 2.7.8 |
Products include Deno Deno.
How do I fix CVE-2026-44726?
Upgrade deno to 2.7.8 or later.
Is CVE-2026-44726 being exploited?
There is no known exploitation of CVE-2026-44726 in the wild and no public exploit code.
Other vulnerabilities in denoland deno
- CVE-2023-28445 Deno improperly handles resizable ArrayBuffer
- CVE-2022-24783 Sandbox bypass leading to arbitrary code execution in Deno
- CVE-2021-32619 Static imports inside dynamically imported modules do not adhere to permission checks
- CVE-2026-22863 Deno node:crypto doesn't finalize cipher
- CVE-2024-27936 Deno interactive permission prompt spoofing via improper ANSI stripping
Sources
Also known as GHSA-chqv-56wv-7564, JLSEC-2026-654.