CVE-2026-26129
CVE-2026-26129 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-138.
Key facts
- Severity: High (CVSS 3.x base score 7.5)
- EPSS exploit prediction: 1% (63rd percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-28445
- Weakness: CWE-138
- Affected product: Microsoft 365 Copilot Chat
- Published:
- Last modified:
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-2026-26129?
- 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-2026-26129?
- CVE-2026-26129 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-2026-26129 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (63rd percentile), an estimate of the probability of exploitation in the next 30 days.
- What products are affected by CVE-2026-26129?
- CVE-2026-26129 affects Microsoft 365 Copilot Chat. See the affected-products list for the exact vulnerable versions.
- How do I fix CVE-2026-26129?
- 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-2026-26129 have an EU (EUVD) identifier?
- Yes. CVE-2026-26129 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28445.
- When was CVE-2026-26129 published?
- CVE-2026-26129 was published on 2026-05-07 and last updated on 2026-06-17.
References
Affected products (1)
- cpe:2.3:a:microsoft:365_copilot_chat:-:*:*:*:*:*:*:*
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- CVE-2025-53787 — High (CVSS 8.2): Microsoft 365 Copilot BizChat Information Disclosure Vulnerability
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