CVE-2026-44296 Deskflow: TLS multiplexer DoS on failed `SSL_accept`
Remote unauthenticated attackers can cause denial of service in Deskflow by sending malformed TLS handshakes, stalling input delivery for all connected users.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-44296?
CVE-2026-44296 is a high-severity denial of service vulnerability in deskflow, published on 12 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Deskflow is a keyboard and mouse sharing app. Prior to 1.26.0.167, a remote, unauthenticated denial of service (DoS) vulnerability affects Deskflow servers running with TLS enabled (the default). When any TCP peer connects to the listening port and its first bytes do not parse as a valid TLS ClientHello, SecureSocket::secureAccept enters its fatal-error branch and calls Arch::sleep(1) (a blocking 1-second sleep) on the multiplexer worker thread. That thread services every socket on the server, including established TLS clients delivering mouse motion, keyboard events, and clipboard updates. A single failed handshake therefore stalls input delivery to all connected screens for ~1 second, and a sustained drip of malformed connections (≥ 1/s) makes the server effectively unusable while the attack persists. This vulnerability is fixed in 1.26.0.167.
Which versions are affected by CVE-2026-44296?
How do I fix CVE-2026-44296?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-44296 being exploited?
There is no known exploitation of CVE-2026-44296 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-44296, GHSA-3mxm-cgh2-6448, UBUNTU-CVE-2026-44296.