CVE-2026-31255: A command injection vulnerability exists in Tenda AC18 V15.03.05.05_multi

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CRITICAL 9.8REMOTEMITIGATE

CVE-2026-31255 is a critical-severity flaw (CVSS 9.8) affecting ac18 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A command injection vulnerability exists in Tenda AC18 V15.03.05.05_multi. The vulnerability is located in the /goform/SetSambaCfg interface, where improper handling of the guestuser parameter allows attackers to execute arbitrary system commands.

Why this priority

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

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.1% (top 34%)
CISA exploited list	No
Weakness	CWE-77
Published	2026-04-27
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: tenda

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

Am I affected?

Timeline

2026-04-27 19:16 UTCPublished CVE record published
2026-06-17 10:33 UTCUpdated Record last modified

tenda ac18 firmware MITIGATE

Affected: 15.03.05.05

Fixed in: no fixed release known

Safe to downgrade to: a release before 15.03.05.05

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.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora 46 · python-python-ulid · FIXED · 4.1.0-2.fc46 · FEDORA-2026-3652e4825b · source

sudo dnf upgrade --advisory=FEDORA-2026-3652e4825b

Fedora ELN · gmp · FIXED · 6.3.0-7.eln159 · FEDORA-2026-1139089b36 · source

sudo dnf upgrade --advisory=FEDORA-2026-1139089b36

Public exploits and detection

Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.

Write-up: github.com/izxnfirh8148/CVE_REQUESTS_references/blob/main/Tenda_AC18/Tenda_AC18_3th/README

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-2026-31255?

ac18 firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-31255 being exploited?

CVE-2026-31255 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-2026-31255 affect?

CVE-2026-31255 affects ac18 firmware. Severity is critical (CVSS 9.8). A command injection vulnerability exists in Tenda AC18 V15.03.05.05_multi. The vulnerability is located in the /goform/SetSambaCfg interface, where improper handling of the guestuser parameter allows attackers to execute arbitrary system co

How urgent is CVE-2026-31255?

Priority 61/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

References

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