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TI-2021-14721 Aliases CVE-2021-36367GHSA-wccm-6vx2-7p8c

PuTTY through 0.75 proceeds with establishing an SSH session even if it has never sent a…

Priority LOW 39CWE-345Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Security bypass
Confidentiality · integrity · availability
High · High · None
Fix status
No fix listed

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA. Impact type from CWE-345.

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).

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.01106 66th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Total

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
——all versions—No fix listedCNA
  • — Vendor— Affected all versions Fixed in — No fix listed CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:putty:putty:*:*:*:*:*:*:*:*up to 0.75VulnerablePuTTY
  • cpe:2.3:a:putty:putty:*:*:*:*:*:*:*:* Versions up to 0.75 Vulnerable ·PuTTY

Remediation

No fixed version listed by the sources yet.

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-36367
  2. 2026-10-03 Alias added: GHSA-wccm-6vx2-7p8c

References

Advisory 2

Other 2

  • TI-2002-01283 Multiple SSH2 servers and clients do not properly handle large packets or large fields… CVSS 2.0HIGH 10.0
  • TI-2023-26623 The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6… CVSS 3.1MEDIUM 5.9
  • TI-2017-04321 The ssh_agent_channel_data function in PuTTY before 0.68 allows remote attackers to have… CVSS 3.0CRITICAL 9.8
  • TI-2026-03565 PuTTY Ed25519 Signature ecc-ssh.c eddsa_verify signature verification CVSS 4.0MEDIUM 6.3
  • TI-2002-01281 Multiple SSH2 servers and clients do not properly handle packets or data elements with… CVSS 2.0HIGH 10.0
  • TI-2004-00914 Integer signedness error in the ssh2_rdpkt function in PuTTY before 0.56 allows remote… CVSS 2.0HIGH 10.0
See all 35 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences