Vulnerability · Published May 21, 2021 · Assigned by mitre
CVE-2021-33500
High 7.5
In plain English
A high-severity security flaw in the putty package (Ubuntu). There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.9% (higher than 80% of all known vulnerabilities).
Severity (CVSS 3.1)7.5High
Exploit odds (30 days)1.9%top 20.1% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known
Official description
PuTTY before 0.75 on Windows allows remote servers to cause a denial of service (Windows GUI hang) by telling the PuTTY window to change its title repeatedly at high speed, which results in many SetWindowTextA or SetWindowTextW calls. NOTE: the same attack methodology may affect some OS-level GUIs on Linux or other platforms for similar reasons.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu:22.04:LTS | putty | no fix listed | UBUNTU-CVE-2021-33500 |
| Ubuntu:24.04:LTS | putty | no fix listed | UBUNTU-CVE-2021-33500 |
| Ubuntu:25.10 | putty | no fix listed | UBUNTU-CVE-2021-33500 |
| Ubuntu:26.04:LTS | putty | no fix listed | UBUNTU-CVE-2021-33500 |
| Ubuntu:26.10 | putty | no fix listed | UBUNTU-CVE-2021-33500 |
Affected products (as reported)
References
- https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html x_refsource_MISC
- https://docs.ssh-mitm.at/puttydos.html x_refsource_MISC
- https://github.com/ssh-mitm/ssh-mitm-plugins/blob/main/ssh_mitm_plugins/ssh/putty_dos.py x_refsource_MISC