How severe is CVE-2026-63509?

CVE-2026-63509 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-63509 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (47th percentile), an estimate of the probability of exploitation in the next 30 days.

How do I fix CVE-2026-63509?

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-2026-63509 published?

CVE-2026-63509 was published on 2026-08-20 and last updated on 2026-08-22.

CVE-2026-63509

CVE-2026-63509 is a critical-severity vulnerability with a CVSS 3.x base score of 9.9. 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-23.

Key facts

Severity: Critical (CVSS 3.x base score 9.9)
EPSS exploit prediction: 1% (47th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-23
Published: 2026-08-20
Last modified: 2026-08-22

Description

Relative path traversal in Microsoft Fabric allows an authorized attacker to elevate privileges over a network.

Frequently asked questions

What is CVE-2026-63509?: Relative path traversal in Microsoft Fabric allows an authorized attacker to elevate privileges over a network.
How severe is CVE-2026-63509?: CVE-2026-63509 has a CVSS 3.x base score of 9.9, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-63509 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (47th percentile), an estimate of the probability of exploitation in the next 30 days.
How do I fix CVE-2026-63509?: 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-2026-63509 published?: CVE-2026-63509 was published on 2026-08-20 and last updated on 2026-08-22.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-63509

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