CVE-2026-89040: Tencent Mass Service Engine in Cluster (MSEC) allows a remote, unauthenticated attacker to send a crafted POST

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CRITICAL 9.8REMOTE

CVE-2026-89040 is a critical-severity flaw (CVSS 9.8) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Tencent Mass Service Engine in Cluster (MSEC) allows a remote, unauthenticated attacker to send a crafted POST request including ../ and gain root access on the target device. An attacker who uploads a webshell can execute arbitrary code as root.

Why this priority

Critical severity
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-22
Published	2026-09-15
Last modified	2026-09-22

Publisher (CNA): Cybersecurity and Infrastructure Security Agency (CISA) U.S. Civilian Government

Last updated 2026-09-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-09-15 20:19 UTCPublished CVE record published
2026-09-22 17:17 UTCUpdated Record last modified

Exact fixes by distribution

Fedora 46 · ddnet · FIXED · 20.2-1.fc46 · FEDORA-2026-6991b4ab14 · source

sudo dnf upgrade --advisory=FEDORA-2026-6991b4ab14

Fedora ELN · libplacebo · FIXED · 7.360.1-5.eln159 · FEDORA-2026-92226f221e · source

sudo dnf upgrade --advisory=FEDORA-2026-92226f221e

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-2026-89040?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-89040 being exploited?

CVE-2026-89040 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-2026-89040 affect?

CVE-2026-89040 affects affected software. Severity is critical (CVSS 9.8). Tencent Mass Service Engine in Cluster (MSEC) allows a remote, unauthenticated attacker to send a crafted POST request including ../ and gain root access on the target device. An attacker who uploads a webshell can execute arbitrary code as

How urgent is CVE-2026-89040?

Priority 56/100. Critical severity; Remotely exploitable, no login, no user action

References

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