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Vulnerability details: VCID-5524-rbbb-xydc
Vulnerability ID VCID-5524-rbbb-xydc
Aliases CVE-2021-36367
Summary PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive authentication response. This makes it easier for an attacker-controlled SSH server to present a later spoofed authentication prompt (that the attacker can use to capture credential data, and use that data for purposes that are undesired by the client user).
Status Published
Exploitability 0.5
Weighted Severity 7.3
Risk 3.6
Affected and Fixed Packages Package Details
Weaknesses (0)
There are no known CWE.
System Score Found at
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
epss 0.00135 https://api.first.org/data/v1/epss?cve=CVE-2021-36367
cvssv3.1 8.1 https://git.tartarus.org/?p=simon/putty.git%3Ba=commit%3Bh=1dc5659aa62848f0aeb5de7bd3839fecc7debefa
ssvc Track https://git.tartarus.org/?p=simon/putty.git%3Ba=commit%3Bh=1dc5659aa62848f0aeb5de7bd3839fecc7debefa
cvssv3.1 8.1 https://lists.debian.org/debian-lts-announce/2024/04/msg00016.html
ssvc Track https://lists.debian.org/debian-lts-announce/2024/04/msg00016.html
archlinux Low https://security.archlinux.org/AVG-2143
cvssv3.1 8.1 https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html
ssvc Track https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html
cvssv3.1 8.1 https://www.debian.org/security/2023/dsa-5588
ssvc Track https://www.debian.org/security/2023/dsa-5588
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2021-36367
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-36367
990901 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=990901
ASA-202107-37 https://security.archlinux.org/ASA-202107-37
AVG-2143 https://security.archlinux.org/AVG-2143
putty.git%3Ba=commit%3Bh=1dc5659aa62848f0aeb5de7bd3839fecc7debefa https://git.tartarus.org/?p=simon/putty.git%3Ba=commit%3Bh=1dc5659aa62848f0aeb5de7bd3839fecc7debefa
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://git.tartarus.org/?p=simon/putty.git%3Ba=commit%3Bh=1dc5659aa62848f0aeb5de7bd3839fecc7debefa
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:T/P:M/B:A/M:M/D:T/2024-02-22T20:07:50Z/ Found at https://git.tartarus.org/?p=simon/putty.git%3Ba=commit%3Bh=1dc5659aa62848f0aeb5de7bd3839fecc7debefa
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://lists.debian.org/debian-lts-announce/2024/04/msg00016.html
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:T/P:M/B:A/M:M/D:T/2024-02-22T20:07:50Z/ Found at https://lists.debian.org/debian-lts-announce/2024/04/msg00016.html
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:T/P:M/B:A/M:M/D:T/2024-02-22T20:07:50Z/ Found at https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.html
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N Found at https://www.debian.org/security/2023/dsa-5588
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: SSVCv2/E:N/A:N/T:T/P:M/B:A/M:M/D:T/2024-02-22T20:07:50Z/ Found at https://www.debian.org/security/2023/dsa-5588
Exploit Prediction Scoring System (EPSS)
Percentile 0.33168
EPSS Score 0.00135
Published At April 1, 2026, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2026-04-01T16:34:57.333916+00:00 Debian Oval Importer Import https://www.debian.org/security/oval/oval-definitions-bullseye.xml.bz2 38.0.0