CVE-2021-27734

Hirschmann HiOS 07.1.01, 07.1.02, and 08.1.00 through 08.5.xx and HiSecOS 03.3.00 through 03.5.01 allow remote attackers to change the credentials of existing users.

Published: 2021-05-17 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-27734 is rated Moderate Risk (48.3/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.11%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-27734

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-03-30 0.27% 0.11% -0.16%
2 2025-03-29 0.08% 0.27% +0.18%
3 2025-03-17 — 0.08% —

Full EPSS history (13 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-27734

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
9.8 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.9 [email protected]
7.5 2.0 HIGH
AV:N/AC:L/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 6.4 [email protected]

Weakness enumeration for CVE-2021-27734

Affected software / configurations for CVE-2021-27734

Vendor Product Version Raw CPE
belden hirschmann_hios >= 08.1.00, < 08.6.00 cpe:2.3:o:belden:hirschmann_hios:*:*:*:*:*:*:*:*
belden hirschmann_hios 07.1.01 cpe:2.3:o:belden:hirschmann_hios:07.1.01:*:*:*:*:*:*:*
belden hirschmann_hios 07.1.02 cpe:2.3:o:belden:hirschmann_hios:07.1.02:*:*:*:*:*:*:*
belden hisecos >= 03.3.00, <= 03.5.01 cpe:2.3:o:belden:hisecos:*:*:*:*:*:*:*:*

References for CVE-2021-27734

cvelogic Threat Intelligence