CVE-2021-27734

9.8 CRITICAL 1% exploit odds Fix listed Auth & access

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.
Exploit odds: 1.3% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2021-05-17 15:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 03:45 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 1.3% in the next 30 days (EPSS).
Severity: 9.8 CRITICAL (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2021-05-17 15:15 UTC
Last modified: 2026-06-17 03:45 UTC
Exploit probability: 1.3% · EPSS, next 30 days
Weakness: CWE-287 · Improper authentication
Record status: Modified

Affected

Belden Hirschmann Hios < 08.6.00
Belden Hirschmann Hios 07.1.01
Belden Hirschmann Hios 07.1.02
Belden Hisecos ≤ 03.5.01

Attack profile CVSS 3.1 · 9.8

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-27734.md and follow it. Check whether this project is affected by CVE-2021-27734. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record