CVE catalog

CVE-2021-33500

putty: CVE-2021-33500

Severity: Low
Source: [NVD] · [CVE record]
EPSS: 1.91% · Oct 25, 2026

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.

Vulnerable and fixed packages

Distribution-reported package versions and fixes. These do not depend on matching against the OpenFactory package catalog.

Distribution	Package	Release	Version	Status
Debian	putty	sid	`0.85-3`	not affected
Debian	putty	forky	`0.85-3`	not affected
Debian	putty	trixie	`0.83-3`	not affected
Debian	putty	bookworm	`0.78-2+deb12u2`	not affected
Debian	putty	bookworm-security	`0.78-2+deb12u1`	not affected

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	putty	source	sid	`Not affected`	unimportant	Not reported	Not reported
Debian	putty	source	forky	`Not affected`	unimportant	Not reported	Not reported
Debian	putty	source	trixie	`Not affected`	unimportant	Not reported	Not reported
Debian	putty	source	bookworm	`Not affected`	unimportant	Not reported	Not reported

OpenFactory catalog packages

[Debian 12 (Bookworm)]

[pterm]Not affected
Source package: [putty]
Details (4)
- 0.78-2+deb12u2 · amd64 · bookworm
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u2 · arm64 · bookworm
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u1 · amd64 · bookworm-security
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u1 · arm64 · bookworm-security
  Not affected
  dsa · putty · debian · bookworm
[putty]Not affected
Details (4)
- 0.78-2+deb12u2 · amd64 · bookworm
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u2 · arm64 · bookworm
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u1 · amd64 · bookworm-security
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u1 · arm64 · bookworm-security
  Not affected
  dsa · putty · debian · bookworm
[putty-doc]Not affected
Source package: [putty]
Details (4)
- 0.78-2+deb12u2 · all · bookworm
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u2 · all · bookworm
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u1 · all · bookworm-security
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u1 · all · bookworm-security
  Not affected
  dsa · putty · debian · bookworm
[putty-tools]Not affected
Source package: [putty]
Details (4)
- 0.78-2+deb12u2 · amd64 · bookworm
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u2 · arm64 · bookworm
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u1 · amd64 · bookworm-security
  Not affected
  dsa · putty · debian · bookworm
- 0.78-2+deb12u1 · arm64 · bookworm-security
  Not affected
  dsa · putty · debian · bookworm

Observed: Oct 23, 2026, 5:57:49 PM UTC

References

[https://security-tracker.debian.org/tracker/CVE-2021-33500]

[Debian Security Tracker] · [FIRST EPSS]