CVE-2021-27891

HIGH

SSH Tectia Client and Server before 6.4.19 on Windows have weak key generation. ConnectSecure on Windows is affected.

Affects 4 products across 2 vendors.

CVSS 3.18.8
EPSS1.1%
Percentile64th
PatchPatched
CVSS Vector — Plain English Remotely exploitable over the network, low complexity, low privileges required, no user interaction needed, impact contained to the vulnerable component, full confidentiality impact, full integrity impact, full availability impact.
◆ AI Analysis — automated analysis, not human-reviewed

SSH Tectia Client and Server before 6.4.19 on Windows, as well as ConnectSecure on Windows, are affected by weak key generation, which could allow attackers to compromise the security of encrypted communications.

BSID: BS-2021-GLOBAL-080733-H • Model: /workspace/models/qwen2.5-coder-32b-instruct-bf16 • Confidence: HIGH

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Frequently Asked Questions
What is CVE-2021-27891?
SSH Tectia Client and Server before 6.4.19 on Windows, as well as ConnectSecure on Windows, are affected by weak key generation, which could allow attackers to compromise the security of encrypted communications.
What is the CVSS score for CVE-2021-27891?
CVE-2021-27891 has CVSS 8.8 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. EPSS: 1.1%.
Is CVE-2021-27891 actively exploited?
No confirmed active exploitation of CVE-2021-27891 as of 2026-05-30.
How do I remediate CVE-2021-27891?
Priority: IMMEDIATE. Advisory: https://info.ssh.com/tectia-vulnerability-cve-2021-27891 PSIRT: [email protected]
What systems are affected by CVE-2021-27891?
CVE-2021-27891 affects Ssh Tectia Server, Tectia Client, Tectia Connectsecure.
Vulnerability Details
CVE IDCVE-2021-27891
BSIDBS-2021-GLOBAL-080733-H BreachSpider Global ID
CVSS VectorCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Published2021-03-15
Last Modified2024-11-21
ICS Relevance0%
SourceNVD
Official Description

SSH Tectia Client and Server before 6.4.19 on Windows have weak key generation. ConnectSecure on Windows is affected.

Source: NIST NVD / MITRE CVE Database

Attack Vector Analysis — CITED Relevance

An attacker could exploit the weak key generation to perform a man-in-the-middle attack, potentially intercepting or altering encrypted data transmitted between the client and server.

Exploitation Likelihood: HIGH

Affected Products
VendorProductAffected Versions
Ssh Tectia Server < 6.4.19
Ssh Tectia Client < 6.4.19
Ssh Tectia Connectsecure No version listed by source

Platforms listed by the source (the vulnerable product runs on these; they are not themselves vulnerable): Microsoft Windows

Remediation
View Vendor Advisory →

Remediation Priority: IMMEDIATE

Vendor PSIRT: [email protected]
Threat Intelligence
● Threat Intelligence Validated: October 2026 | Threat Age: 2040 Days
CISA known-exploitedNot in KEV catalog
Public ExploitNot confirmed
PoC CodeNot confirmed
AI Enrichment Record — provenance & audit hash
Model/workspace/models/qwen2.5-coder-32b-instruct-bf16
ConfidenceHIGH
Enriched At2026-05-24
SHA-512 Audit Hash6ad7e53c1fb2a3d1ee5f1a231c443bda96a6f67756b5881ee40329e58abaf655f90f8d50fef4f6e7937919bda1ee0205f6d980423f151bdb01c02ffbeb2d0e07
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