{"id":"CVE-2021-36367","aliases":["ALPINE-CVE-2021-36367","DEBIAN-CVE-2021-36367","DLA-3794-1","EUVD-2021-22987","GHSA-wccm-6vx2-7p8c","UBUNTU-CVE-2021-36367"],"status":"published","title":"PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a...","description":"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).","severity":{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"high","assessor":"primary","from":"nvd"},"epss":{"day":"2026-11-10","score":0.01106,"percentile":0.66102,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-345"],"published":"2021-07-09T00:00:00Z","modified":"2026-11-03T06:31:42Z","fixes":[{"ecosystem":"Alpine:v3.11","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.12","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.13","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.14","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.15","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.16","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.17","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.18","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.19","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.20","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.21","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.22","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.23","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Alpine:v3.24","package":"putty","fixed_in":["0.76-r0"],"sources":["osv"]},{"ecosystem":"Debian:12","package":"putty","fixed_in":["0.75-3"],"sources":["osv"]},{"ecosystem":"Debian:13","package":"putty","fixed_in":["0.75-3"],"sources":["osv"]},{"ecosystem":"Debian:14","package":"putty","fixed_in":["0.75-3"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Alpine:v3.11","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.12","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.13","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.14","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.15","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.16","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.17","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.18","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.19","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.20","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.21","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.22","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.23","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Alpine:v3.24","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.76-r0"}]}]},{"source":"osv","ecosystem":"Debian:12","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.75-3"}]}]},{"source":"osv","ecosystem":"Debian:13","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.75-3"}]}]},{"source":"osv","ecosystem":"Debian:14","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.75-3"}]}]},{"source":"osv","ecosystem":"Debian:10","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.74-1+deb11u1~deb10u1"}]}],"versions":["0.70-6","0.71-1","0.72-1","0.72-2","0.73-1","0.73-2","0.73-3","0.74-1"],"bundled":4},{"source":"osv","ecosystem":"Ubuntu:16.04:LTS","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.65-2","0.66-1","0.66-2","0.66-3","0.66-4","0.67-1","0.67-2","0.67-3build0.16.04.1","0.67-3+deb9u1build0.16.04.1"]},{"source":"osv","ecosystem":"Ubuntu:18.04:LTS","package":"putty","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]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Notes","Third Party Advisory","advisory","report"]},{"url":"https://git.tartarus.org/?p=simon/putty.git%3Ba=commit%3Bh=1dc5659aa62848f0aeb5de7bd3839fecc7debefa","tags":["x_transferred","web"]},{"url":"https://www.debian.org/security/2023/dsa-5588","tags":["vendor-advisory","x_transferred","advisory"]},{"url":"https://lists.debian.org/debian-lts-announce/2024/04/msg00016.html","tags":["mailing-list","x_transferred","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-36367"},{"url":"https://git.tartarus.org/?p=simon/putty.git;a=commit;h=1dc5659aa62848f0aeb5de7bd3839fecc7debefa","tags":["report"]},{"url":"https://github.com/advisories/GHSA-wccm-6vx2-7p8c"},{"url":"https://security.alpinelinux.org/vuln/CVE-2021-36367","tags":["advisory"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2021-36367","tags":["advisory"]},{"url":"https://ubuntu.com/security/CVE-2021-36367","tags":["report"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2021-36367","tags":["report"]}],"sources":{"cve":[{"id":"CVE-2021-36367","description":"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","published":"2021-07-09T00:00:00Z","modified":"2024-08-04T00:54:51.472Z","cvss":[{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"high","assessor":"adp"}],"cwes":["CWE-345"],"updated_at":"2026-11-02T14:33:06.32268Z"}],"euvd":[{"id":"EUVD-2021-22987","description":"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","published":"2021-07-09T00:00:00Z","modified":"2024-08-04T00:54:51Z","cvss":[{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"high"}],"updated_at":"2026-11-03T03:24:29.877227Z"}],"ghsa":[{"id":"GHSA-wccm-6vx2-7p8c","title":"PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a...","description":"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","published":"2022-05-24T19:07:19Z","modified":"2024-04-26T00:30:35Z","cvss":[{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"high"}],"cwes":["CWE-345"],"updated_at":"2026-11-02T14:57:14.537163Z"}],"nvd":[{"id":"CVE-2021-36367","description":"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","published":"2021-07-09T21:15:08.54Z","modified":"2026-06-17T03:58:45.173Z","cvss":[{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"high","assessor":"primary"},{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"high","assessor":"secondary"},{"version":"2.0","score":5.8,"vector":"AV:N/AC:M/Au:N/C:P/I:P/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-345"],"updated_at":"2026-11-02T14:06:55.259633Z"}],"osv":[{"id":"ALPINE-CVE-2021-36367","description":"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","published":"2021-07-09T21:15:08.54Z","modified":"2026-11-03T06:31:42.404399613Z","cvss":[{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"high"}],"updated_at":"2026-11-03T07:18:15.355745Z"},{"id":"CVE-2021-36367","description":"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","published":"2021-07-09T21:15:08.54Z","modified":"2026-03-15T22:37:24.480412Z","cvss":[{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T15:44:20.434873Z"},{"id":"DEBIAN-CVE-2021-36367","description":"PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a substantive authentication response. 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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","published":"2021-07-09T21:15:00Z","modified":"2025-10-24T04:50:26Z","cvss":[{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"high"},{"version":"3.1","score":8.1,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T15:54:27.870979Z"},{"id":"DLA-3794-1","title":"putty - security update","status":"published","published":"2024-04-25T00:00:00Z","modified":"2026-03-09T01:19:59.551509Z","updated_at":"2026-11-02T15:46:12.203458Z"}]}}