How severe is CVE-2026-26164?

CVE-2026-26164 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.

Is CVE-2026-26164 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (52nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-26164?

CVE-2026-26164 affects Microsoft 365 Copilot Chat. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-26164?

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

Does CVE-2026-26164 have an EU (EUVD) identifier?

Yes. CVE-2026-26164 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28446.

When was CVE-2026-26164 published?

CVE-2026-26164 was published on 2026-05-07 and last updated on 2026-06-17.

CVE-2026-26164

CVE-2026-26164 is a high-severity vulnerability in Microsoft 365 Copilot Chat with a CVSS 3.x base score of 7.5. 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-74.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 1% (52nd percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-28446
Weakness: CWE-74
Affected product: Microsoft 365 Copilot Chat
Published: 2026-05-07
Last modified: 2026-06-17

Description

Improper neutralization of special elements used in a command ('command injection') in M365 Copilot allows an unauthorized attacker to disclose information over a network.

Frequently asked questions

What is CVE-2026-26164?: Improper neutralization of special elements used in a command ('command injection') in M365 Copilot allows an unauthorized attacker to disclose information over a network.
How severe is CVE-2026-26164?: CVE-2026-26164 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity none, and availability none.
Is CVE-2026-26164 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (52nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-26164?: CVE-2026-26164 affects Microsoft 365 Copilot Chat. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-26164?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-26164 have an EU (EUVD) identifier?: Yes. CVE-2026-26164 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28446.
When was CVE-2026-26164 published?: CVE-2026-26164 was published on 2026-05-07 and last updated on 2026-06-17.

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-26164

Affected products (1)

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

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