CVE catalog

CVE-2021-36367

putty: CVE-2021-36367

Severity: Medium
Published: Jul 9, 2021, 9:15:00 PM UTC
Source: [NVD] · [CVE record]
EPSS: 1.11% · Oct 25, 2026

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).

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`	fixed
Debian	putty	forky	`0.85-3`	fixed
Debian	putty	trixie	`0.83-3`	fixed
Debian	putty	bookworm	`0.78-2+deb12u2`	fixed
Debian	putty	bookworm-security	`0.78-2+deb12u1`	fixed
Alpine	putty	3.11	`0.76-r0`	fixed
Alpine	putty	3.12	`0.76-r0`	fixed
Alpine	putty	3.13	`0.76-r0`	fixed
Alpine	putty	3.14	`0.76-r0`	fixed
Alpine	putty	3.15	`0.76-r0`	fixed
Alpine	putty	3.16	`0.76-r0`	fixed
Alpine	putty	3.17	`0.76-r0`	fixed
Alpine	putty	3.18	`0.76-r0`	fixed
Alpine	putty	3.19	`0.76-r0`	fixed
Ubuntu	putty	16.04	`0.65-2`	vulnerable
Ubuntu	putty	16.04	`0.66-1`	vulnerable
Ubuntu	putty	16.04	`0.66-2`	vulnerable
Ubuntu	putty	16.04	`0.66-3`	vulnerable
Ubuntu	putty	16.04	`0.66-4`	vulnerable
Ubuntu	putty	16.04	`0.67-1`	vulnerable
Ubuntu	putty	16.04	`0.67-2`	vulnerable
Ubuntu	putty	16.04	`0.67-3build0.16.04.1`	vulnerable
Ubuntu	putty	16.04	`0.67-3+deb9u1build0.16.04.1`	vulnerable
Ubuntu	putty	18.04	`0.70-1`	vulnerable
Ubuntu	putty	18.04	`0.70-2`	vulnerable
Ubuntu	putty	18.04	`0.70-3`	vulnerable
Ubuntu	putty	18.04	`0.70-4`	vulnerable
Ubuntu	putty	20.04	`0.72-1`	vulnerable
Ubuntu	putty	20.04	`0.73-1`	vulnerable
Ubuntu	putty	20.04	`0.73-2`	vulnerable
Ubuntu	putty	22.04	`0.75-3`	vulnerable
Ubuntu	putty	22.04	`0.76-1`	vulnerable
Ubuntu	putty	22.04	`0.76-2`	vulnerable

Fixed-version evidence

Distribution	Package	Type	Release	Fixed version	Urgency	Origin	Bugs
Debian	putty	source	sid	`0.75-3`	not yet assigned	Not reported	[990901]
Debian	putty	source	forky	`0.75-3`	not yet assigned	Not reported	[990901]
Debian	putty	source	trixie	`0.75-3`	not yet assigned	Not reported	[990901]
Debian	putty	source	bookworm	`0.75-3`	not yet assigned	Not reported	[990901]
Alpine	putty	apk	3.11	`0.76-r0`	Not reported	ALPINE-CVE-2021-36367	Not reported
Alpine	putty	apk	3.12	`0.76-r0`	Not reported	ALPINE-CVE-2021-36367	Not reported
Alpine	putty	apk	3.13	`0.76-r0`	Not reported	ALPINE-CVE-2021-36367	Not reported
Alpine	putty	apk	3.14	`0.76-r0`	Not reported	ALPINE-CVE-2021-36367	Not reported
Alpine	putty	apk	3.15	`0.76-r0`	Not reported	ALPINE-CVE-2021-36367	Not reported
Alpine	putty	apk	3.16	`0.76-r0`	Not reported	ALPINE-CVE-2021-36367	Not reported
Alpine	putty	apk	3.17	`0.76-r0`	Not reported	ALPINE-CVE-2021-36367	Not reported
Alpine	putty	apk	3.18	`0.76-r0`	Not reported	ALPINE-CVE-2021-36367	Not reported
Alpine	putty	apk	3.19	`0.76-r0`	Not reported	ALPINE-CVE-2021-36367	Not reported

[Debian bug #990901]

OpenFactory catalog packages

[Debian 12 (Bookworm)]

[pterm]Fixed
Source package: [putty]
Details (4)
- 0.78-2+deb12u2 · amd64 · bookworm
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u2 · arm64 · bookworm
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u1 · amd64 · bookworm-security
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u1 · arm64 · bookworm-security
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
[putty]Fixed
Details (4)
- 0.78-2+deb12u2 · amd64 · bookworm
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u2 · arm64 · bookworm
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u1 · amd64 · bookworm-security
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u1 · arm64 · bookworm-security
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
[putty-doc]Fixed
Source package: [putty]
Details (4)
- 0.78-2+deb12u2 · all · bookworm
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u2 · all · bookworm
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u1 · all · bookworm-security
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u1 · all · bookworm-security
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
[putty-tools]Fixed
Source package: [putty]
Details (4)
- 0.78-2+deb12u2 · amd64 · bookworm
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u2 · arm64 · bookworm
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u1 · amd64 · bookworm-security
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12
- 0.78-2+deb12u1 · arm64 · bookworm-security
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · bookworm; dsa · putty · debian · 12

[Debian 13 (Trixie)]

[pterm]Fixed
Source package: [putty]
Details (2)
- 0.83-3 · amd64 · trixie
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · 13
- 0.83-3 · arm64 · trixie
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · 13
[putty]Fixed
Details (2)
- 0.83-3 · amd64 · trixie
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · 13
- 0.83-3 · arm64 · trixie
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · 13
[putty-doc]Fixed
Source package: [putty]
Details (2)
- 0.83-3 · all · trixie
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · 13
- 0.83-3 · all · trixie
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · 13
[putty-tools]Fixed
Source package: [putty]
Details (2)
- 0.83-3 · amd64 · trixie
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · 13
- 0.83-3 · arm64 · trixie
  Fixed · Fixed: 0.75-3
  dsa · putty · debian · 13

Observed: Oct 23, 2026, 5:58:46 PM UTC

References

[CERT-Bund public advisories] · [Debian Security Tracker] · [FIRST EPSS] · [OSV Package Vulnerability Database]