High severity · published May 21, 2021
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…
7.5
CVSS
1.9%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)1.9% · higher than 80% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PU
Putty · Putty
before 0.75 · source: NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-33500
CVE.org
https://www.cve.org/CVERecord?id=CVE-2021-33500
Exploit
https://docs.ssh-mitm.at/puttydos.html
Exploit
https://github.com/ssh-mitm/ssh-mitm-plugins/blob/main/ssh_mitm_plugins/ssh/putty_dos.py
Release Notes
https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html
More from Putty
9.8
CVE-2019-17067
PuTTY before 0.73 on Windows improperly opens port-forwarding listening sockets, which allows attackers to listen on the same port to steal an incoming connection
9.8
CVE-2019-9898
Potential recycling of random numbers used in cryptography exists within PuTTY before 0.71
9.8
CVE-2019-9895
In PuTTY versions before 0.71 on Unix, a remotely triggerable buffer overflow exists in any kind of server-to-client forwarding
9.8
CVE-2017-6542
The ssh_agent_channel_data function in PuTTY before 0.68 allows remote attackers to have unspecified impact via a large length value in an agent protocol message and leveraging…
8.1
CVE-2021-36367
PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive authentication response