CVE-2021-33500
CVSS v3
7.5
HIGH
EPSS Score
2.0 %
exploit probability, as of 2026-09-25
CISA KEV
No
known exploited
Exploitation
—
SSVC status
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.
Technical details
- Published
- 2021-05-21
Frequently asked questions
What is 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.
Is CVE-2021-33500 actively exploited?
Active exploitation of CVE-2021-33500 has not been confirmed. Its EPSS score was 2.0% on 2026-09-25, the estimated probability of exploitation in the next 30 days.
What is the CVSS score for CVE-2021-33500?
CVE-2021-33500 has a CVSS v3 base score of 7.5 (HIGH severity).
Is CVE-2021-33500 affecting your environment?
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