CVE-2026-26129: Improper neutralization of special elements in M365 Copilot allows an unauthorized attacker to disclose information over
highvulnerabilityLLM-Specific
security
Summary
CVE-2026-26129 is a vulnerability in Microsoft 365 Copilot where improper neutralization of special elements (failure to safely handle certain characters or code) allows an unauthorized attacker to disclose information over a network. The vulnerability has a CVSS score (a 0-10 rating of how severe a vulnerability is) of 4.0, indicating moderate severity.
Vulnerability Details
CVSS Score
7.5(high)
EPSS (30-day exploit probability)
EPSS: 0.0%
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
Attack Vector
network
Attack Complexity
low
Privileges Required
none
User Interaction
none
Disclosure Date
May 7, 2026
Classification
Attack Type
PII Leakage
Attack SophisticationModerate
Impact (CIA+S)
confidentiality
AI Component TargetedAPI
Taxonomy References
CWE (Weakness Type)
Affected Vendors
Microsoft
Related Issues
Monthly digest — independent AI security research
Original source: https://nvd.nist.gov/vuln/detail/CVE-2026-26129
First tracked: May 7, 2026 at 08:08 PM
Classified by LLM (prompt v3) · confidence: 85%