CVE-2021-26731: Command injection and multiple stack-based buffer overflows vulnerabilities in the modifyUserb_func function o

This month

CRITICAL 9.1MITIGATE

CVE-2021-26731 is a critical-severity flaw (CVSS 9.1) affecting iac-ast2500a firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Command injection and multiple stack-based buffer overflows vulnerabilities in the modifyUserb_func function of spx_restservice allow an authenticated attacker to execute arbitrary code with the same privileges as the server user (root). This issue affects: Lanner Inc IAC-AST2500A standard firmware version 1.10.0.

Why this priority

Critical severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.1 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	High
User interaction	None
EPSS exploit chance	2.7% (top 14%)
CISA exploited list	No
Weakness	CWE-94, CWE-121, CWE-77, CWE-787
Published	2022-10-24
Last modified	2026-06-17

Publisher (CNA): Nozomi Networks Inc. · Vendor: lannerinc

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

Am I affected?

Timeline

2022-10-24 14:15 UTCPublished CVE record published
2026-06-17 03:43 UTCUpdated Record last modified

lannerinc iac-ast2500a firmware MITIGATE

Affected: 1.10.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.10.0

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-2021-26731?

iac-ast2500a firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-26731 being exploited?

CVE-2021-26731 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-2021-26731 affect?

CVE-2021-26731 affects iac-ast2500a firmware. Severity is critical (CVSS 9.1). Command injection and multiple stack-based buffer overflows vulnerabilities in the modifyUserb_func function of spx_restservice allow an authenticated attacker to execute arbitrary code with the same privileges as the server user (root). Th

How urgent is CVE-2021-26731?

Priority 53/100. Critical severity

Related CVEs

CVE-2021-46279 MEDIUM 5.8 MITIGATE Session fixation and insufficient session expiration vulnerabilities allow an attacker to perfom session hijac
CVE-2021-45925 MEDIUM 5.3 MITIGATE Observable discrepancies in the login process allow an attacker to guess legitimate user names registered in t
CVE-2021-44776 MEDIUM 6.5 MITIGATE A broken access control vulnerability in the SubNet_handler_func function of spx_restservice allows an attacke
CVE-2021-44769 MEDIUM 4.9 MITIGATE An improper input validation vulnerability in the TLS certificate generation function allows an attacker to ca
CVE-2021-44467 MEDIUM 5.3 MITIGATE A broken access control vulnerability in the KillDupUsr_func function of spx_restservice allows an attacker to

References

← Back to latest CVEs