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).
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | putty | 0.75-3 | — |
| Debian 13 | putty | 0.75-3 | — |
| Debian 12 | putty | 0.75-3 | — |
| Debian 10 | putty | 0.74-1+deb11u1~deb10u1 | DLA-3794-1 |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 22.04 LTS | putty | No fix yet | — |
| Ubuntu 20.04 LTS | putty | No fix yet | — |
| Ubuntu 18.04 LTS | putty | No fix yet | — |
| Ubuntu 16.04 LTS | putty | No fix yet | — |
Alpine
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.24 | putty | 0.76-r0 | — |
| Alpine v3.23 | putty | 0.76-r0 | — |
| Alpine v3.22 | putty | 0.76-r0 | — |
| Alpine v3.21 | putty | 0.76-r0 | — |
| Alpine v3.20 | putty | 0.76-r0 | — |
Show 9 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Alpine v3.19 | putty | 0.76-r0 | — |
| Alpine v3.18 | putty | 0.76-r0 | — |
| Alpine v3.17 | putty | 0.76-r0 | — |
| Alpine v3.16 | putty | 0.76-r0 | — |
| Alpine v3.15 | putty | 0.76-r0 | — |
| Alpine v3.14 | putty | 0.76-r0 | — |
| Alpine v3.13 | putty | 0.76-r0 | — |
| Alpine v3.12 | putty | 0.76-r0 | — |
| Alpine v3.11 | putty | 0.76-r0 | — |
Advisories 2
- DLA-3794-1 putty - security update Debian Security (DSA / DLA) · Mar 9, 2026
- WID-SEC-2023-3218 PuTTY: Schwachstelle ermöglicht Umgehen von Sicherheitsvorkehrungen BSI CERT-Bund (WID) · Apr 25, 2024