8.1

CVE-2021-36367: putty

Modified
AliasesALPINE-CVE-2021-36367UBUNTU-CVE-2021-36367DEBIAN-CVE-2021-36367
Published 09-07-2021Last modified 04-08-2024

Vulnerability summary

CVE-2021-36367 is a high (CVSS 8.1) vulnerability in putty. EPSS estimates a 1.11% chance of exploitation in the next 30 days, higher than 65.8% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 8.1, network access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
8.1/10
010
High · v3.1 (CVE.org)
EPSS score
1.11%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 1
DLA-3794-1

Timeline

  1. 09-07-2021
    PublishedVulnerability first disclosed.
  2. 04-08-2024
    Last modifiedVulnerability information updated.

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).

CVSS metrics

6 scores · 5 sources · 2 versions

EPSS trend

Probability

1.11%

Chance of exploitation in the next 30 days

Percentile

66%

Versus all other CVEs

30-day change

No change 0.00 pp

From 1.11% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.

Alpine1 product
  • putty< 0.76-r0
Debian1 product
  • putty< 0.75-3
Putty1 product
Ubuntu1 product
  • puttyAll versions (No fix recorded)

4 vendors · 4 products

References

9 links