Vulnerability Monitor

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CVE-2021-33500

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.

Security Impact Summary

This vulnerability carries a HIGH severity rating with a CVSS v3.1 score of 7.5, indicating it can be exploited remotely over the network with relatively low complexity without requiring user interaction and does not require pre-existing privileges . The vulnerability impacts and availability (service disruption) for affected systems. Impacting 2 products from putty, from microsoft organizations running these solutions should prioritize assessment and patching.

Historical Context

Reported in 2021, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.

Published

2021-05-21T20:15:07.723

Last Modified

2024-11-21T06:08:57.423

Status

Modified

Source

[email protected]

Severity

CVSSv3.1: 7.5 (HIGH)

CVSSv2 Vector

AV:N/AC:L/Au:N/C:N/I:N/A:P

Access Vector: NETWORK
Access Complexity: LOW
Authentication: NONE
Confidentiality Impact: NONE
Integrity Impact: NONE
Availability Impact: PARTIAL

Exploitability Score

10.0

Impact Score

2.9

Weaknesses

Type: Primary
NVD-CWE-noinfo

Affected Vendors & Products

Type	Vendor	Product	Version/Range	Vulnerable?
Application	putty	putty	< 0.75	Yes
Operating System	microsoft	windows	-	No

References

https://docs.ssh-mitm.at/puttydos.html Exploit, Third Party Advisory ([email protected])
https://github.com/ssh-mitm/ssh-mitm-plugins/blob/main/ssh_mitm_plugins/ssh/putty_dos.py Exploit, Third Party Advisory ([email protected])
https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html Release Notes, Third Party Advisory ([email protected])
https://docs.ssh-mitm.at/puttydos.html Exploit, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://github.com/ssh-mitm/ssh-mitm-plugins/blob/main/ssh_mitm_plugins/ssh/putty_dos.py Exploit, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)
https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html Release Notes, Third Party Advisory (af854a3a-2127-422b-91ae-364da2661108)

How SecUtils Interprets This CVE

SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For putty's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.