CVE-2023-26921: OS Command Injection vulnerability in quectel AG550QCN allows attackers to execute arbitrary commands via ql_a

This week

CRITICAL 9.8REMOTEMITIGATE

CVE-2023-26921 is a critical-severity flaw (CVSS 9.8) affecting ag550qcn firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

OS Command Injection vulnerability in quectel AG550QCN allows attackers to execute arbitrary commands via ql_atfwd.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

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

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.7% (top 14%)
CISA exploited list	No
Weakness	CWE-78
Published	2023-04-04
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: quectel

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

Am I affected?

Timeline

2023-04-04 15:15 UTCPublished CVE record published
2026-06-17 05:43 UTCUpdated Record last modified

quectel ag550qcn firmware MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

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-2023-26921?

ag550qcn firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2023-26921 being exploited?

CVE-2023-26921 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-2023-26921 affect?

CVE-2023-26921 affects ag550qcn firmware. Severity is critical (CVSS 9.8). OS Command Injection vulnerability in quectel AG550QCN allows attackers to execute arbitrary commands via ql_atfwd.

How urgent is CVE-2023-26921?

Priority 66/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

References

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