CVE-2021-47764 AbsoluteTelnet 11.24 - 'Phone' Denial of Service (PoC)

Medium 6.7 Published 15 Jan 2026 Updated 1 Oct 2026

Local attackers can crash AbsoluteTelnet by pasting long payloads into DialUp and license fields, causing application termination.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Local or same network only
Victim action needed: A user has to click or open something
Fix: None listed

What is CVE-2021-47764?

CVE-2021-47764 is a medium-severity denial of service vulnerability in Celestialsoftware AbsoluteTelnet, published on 15 Jan 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

Official description

AbsoluteTelnet 11.24 contains a denial of service vulnerability that allows local attackers to crash the application by manipulating DialUp connection and license name fields. Attackers can generate a 1000-character payload and paste it into specific input fields to trigger application crashes and force unexpected termination.

Weakness: CWE-787

Which versions are affected by CVE-2021-47764?

It affects 1 product.

Products include Celestialsoftware Absolutetelnet.

How do I fix CVE-2021-47764?

No fix has been published for CVE-2021-47764 yet. Limit exposure of the affected software until one is available.

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-2021-47764 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2021-47764 exists.

Sources

Also known as GHSA-g9m3-654m-8943.