CVE-2021-33903: In LCOS 10.40 to 10.42.0473-RU3 with SNMPv3 enabled on LANCOM devices, changing the password of the root user

Q: How do I fix CVE-2021-33903?

lcos: upgrade to 10.42.0473. Exact commands for each OS are on this page.

Q: Is CVE-2021-33903 being exploited?

CVE-2021-33903 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-33903 affect?

CVE-2021-33903 affects lcos. Severity is high (CVSS 8.8). In LCOS 10.40 to 10.42.0473-RU3 with SNMPv3 enabled on LANCOM devices, changing the password of the root user via the CLI does not change the password of the root user for SNMPv3 access. (However, changing the password of the root user via

This month

HIGH 8.8UPGRADE

CVE-2021-33903 is a high-severity flaw (CVSS 8.8) affecting lcos. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

In LCOS 10.40 to 10.42.0473-RU3 with SNMPv3 enabled on LANCOM devices, changing the password of the root user via the CLI does not change the password of the root user for SNMPv3 access. (However, changing the password of the root user via LANconfig does change the password of the root user for SNMPv3 access.)

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	1.1% (top 34%)
CISA exploited list	No
Published	2021-10-07
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: lancom-systems

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-10-07 15:15 UTCPublished CVE record published
2026-06-17 03:55 UTCUpdated Record last modified

lancom-systems lcos UPGRADE

Affected: >= 10.40 and < 10.42.0473 · 10.42.0473 · 10.42.0473 release_update1 · 10.42.0473 release_update2 · 10.42.0473 release_update3

Fixed in: 10.42.0473

Safe to downgrade to: a release before 10.40

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-33903?

lcos: upgrade to 10.42.0473. Exact commands for each OS are on this page.

Is CVE-2021-33903 being exploited?

CVE-2021-33903 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-33903 affect?

CVE-2021-33903 affects lcos. Severity is high (CVSS 8.8). In LCOS 10.40 to 10.42.0473-RU3 with SNMPv3 enabled on LANCOM devices, changing the password of the root user via the CLI does not change the password of the root user for SNMPv3 access. (However, changing the password of the root user via

How urgent is CVE-2021-33903?

Priority 47/100. High severity

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References

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