How severe is CVE-2026-84411?

CVE-2026-84411 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-84411 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-84411?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2026-84411 published?

CVE-2026-84411 was published on 2026-10-02 and last updated on 2026-10-06.

CVE-2026-84411

CVE-2026-84411 is a critical-severity vulnerability with a CVSS 3.x base score of 9.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-191.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v4: 9.3
EPSS exploit prediction: 1% (60th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-191
Published: 2026-10-02
Last modified: 2026-10-06

Description

The web management service in affected RouterOS versions contains an integer underflow in its HTTP request body handling that is reachable before authentication. This can be leveraged by an unauthenticated network attacker to achieve arbitrary code execution as root, or to cause a denial of service, using a single crafted request.

Frequently asked questions

What is CVE-2026-84411?: The web management service in affected RouterOS versions contains an integer underflow in its HTTP request body handling that is reachable before authentication. This can be leveraged by an unauthenticated network attacker to achieve arbitrary code execution as root, or to cause a denial of service, using a single crafted request.
How severe is CVE-2026-84411?: CVE-2026-84411 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-84411 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (60th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-84411?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2026-84411 published?: CVE-2026-84411 was published on 2026-10-02 and last updated on 2026-10-06.

References

Other CWE-191 (Integer Underflow) vulnerabilities

CVE-2007-0063 — Critical (CVSS 10.0): Integer underflow in the DHCP server in EMC VMware Workstation before 5.5.5 Build 56455 and 6.x before 6.0.1 Build…
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CVE-2026-51540 — Critical (CVSS 9.8): OpENer 2.3.0 (master branch up to commit 76b95cf) is vulnerable to a severe memory corruption issue caused by an…
CVE-2026-53176 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: IB/isert: Reject login PDUs shorter than…
CVE-2026-37534 — Critical (CVSS 9.8): Integer underflow vulnerability in Open-SAE-J1939 thru commit b6caf884df46435e539b1ecbf92b6c29b345bdfe (2025-11-30) in…
CVE-2025-52471 — Critical (CVSS 9.8): ESF-IDF is the Espressif Internet of Things (IOT) Development Framework. An integer underflow vulnerability has been…

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