Security readout for executives and security teams
Plain-English summary
A malicious SSH server can trick vulnerable PuTTY clients into continuing an SSH session without a real authentication exchange, then show a spoofed prompt to capture credentials. It requires a user to connect to an attacker-controlled or compromised server. Business risk is credential theft and downstream access, not direct server compromise of the PuTTY host.
Executive priority
Prioritize remediation for administrators and teams handling privileged SSH access. The issue can lead to credential theft through social deception during SSH use, with high downstream impact if privileged credentials are captured.
Technical view
PuTTY through 0.75 mishandles SSH authentication state and may establish a session after no substantive authentication response. CVSS 3.1 is 8.1 with user interaction required, mapped to CWE-345. Attack surface is client-side SSH connections to untrusted server endpoints; impact centers on confidentiality and integrity of captured credentials.
Likely exposure
Exposure is likely where users run PuTTY 0.75 or earlier, especially unmanaged administrator workstations, jump hosts, and legacy Debian systems. The bundle does not identify specific CPEs or non-PuTTY products.
Exploitation context
The source bundle does not show CISA KEV listing or confirmed active exploitation. Exploitation requires user interaction: a vulnerable client must connect to an attacker-controlled SSH server that can present a misleading later prompt.
Researcher notes
Evidence identifies an authentication-state flaw in PuTTY through 0.75 and references an upstream commit plus Debian advisories. The bundle lacks exploit-in-the-wild evidence, detailed affected package matrices, and explicit fixed version text, so validation should rely on vendor and distribution advisory data.
Mitigation direction
- Inventory PuTTY versions on administrator workstations and jump hosts.
- Update PuTTY from affected releases using vendor or OS security guidance.
- Apply Debian security updates where PuTTY is installed from Debian packages.
- Warn users not to trust unexpected password prompts from unfamiliar SSH servers.
- Review credential exposure if users connected to suspicious SSH endpoints.
Validation and detection
- Confirm installed PuTTY versions are later than the affected through-0.75 range.
- Check Debian package status against DSA-5588 and DLA-3794-1.
- Review endpoint inventory for portable or unmanaged PuTTY copies.
- Look for recent connections to unknown or suspicious SSH servers.
- Verify users report unexpected SSH authentication prompts for investigation.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-345: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCredential and access behavior lookup
The CVE wording references authentication or credential exposure, so valid-account and credential-access review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-36367 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N2.85.2Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.1HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://www.chiark.greenend.org.uk/~sgtatham/putty/changes.htmlCVE reference
- https://git.tartarus.org/?p=simon/putty.git%3Ba=commit%3Bh=1dc5659aa62848f0aeb5de7bd3839fecc7debefaCVE reference
- DSA-5588CVE reference · vendor-advisory
- [debian-lts-announce] 20240425 [SECURITY] [DLA 3794-1] putty security updateCVE reference · mailing-list
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Insufficient Verification of Data Authenticity
Insufficient Verification of Data Authenticity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.