CVE-2026-26129

HIGH
Published May 7, 2026 Modified May 8, 2026 CWE-138

Description

Improper neutralization of special elements in M365 Copilot allows an unauthorized attacker to disclose information over a network.

CVSS v3.1 Score

7.5
HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

EPSS — Exploit Prediction

0.0006
Probability of exploitation
0.18%
Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-138 CWE-138

Affected Products

Vendor Product
microsoft 365_copilot_chat

References

Frequently Asked Questions

What is CVE-2026-26129? +
Improper neutralization of special elements in M365 Copilot allows an unauthorized attacker to disclose information over a network. It has a CVSS v3.1 base score of 7.5 (HIGH).
How severe is CVE-2026-26129? +
CVE-2026-26129 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0006, placing it in the 0th percentile for exploitation probability.
What products are affected by CVE-2026-26129? +
CVE-2026-26129 affects products from microsoft, specifically: 365_copilot_chat. Check the affected products table above for specific version ranges.
How do I check if I'm vulnerable to CVE-2026-26129? +
You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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