How severe is CVE-2026-26137?

CVE-2026-26137 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 low.

Is CVE-2026-26137 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (41st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-26137?

CVE-2026-26137 affects Microsoft 365 Copilot Chat. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-26137?

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.

Does CVE-2026-26137 have an EU (EUVD) identifier?

Yes. CVE-2026-26137 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13184.

When was CVE-2026-26137 published?

CVE-2026-26137 was published on 2026-03-19 and last updated on 2026-06-17.

CVE-2026-26137

CVE-2026-26137 is a critical-severity vulnerability in Microsoft 365 Copilot Chat 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-918.

Key facts

Severity: Critical (CVSS 3.x base score 9.9)
EPSS exploit prediction: 1% (41st percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-13184
Weakness: CWE-918
Affected product: Microsoft 365 Copilot Chat
Published: 2026-03-19
Last modified: 2026-06-17

Description

Server-side request forgery (ssrf) in Microsoft Exchange allows an authorized attacker to elevate privileges over a network.

Frequently asked questions

What is CVE-2026-26137?: Server-side request forgery (ssrf) in Microsoft Exchange allows an authorized attacker to elevate privileges over a network.
How severe is CVE-2026-26137?: CVE-2026-26137 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 low.
Is CVE-2026-26137 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (41st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-26137?: CVE-2026-26137 affects Microsoft 365 Copilot Chat. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-26137?: 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.
Does CVE-2026-26137 have an EU (EUVD) identifier?: Yes. CVE-2026-26137 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-13184.
When was CVE-2026-26137 published?: CVE-2026-26137 was published on 2026-03-19 and last updated on 2026-06-17.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26137

Affected products (1)

cpe:2.3:a:microsoft:365_copilot_chat:-:*:*:*:*:*:*:*

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