CVE-2026-21509
Reliance on untrusted inputs in a security decision in Microsoft Office allows an unauthorized attacker to bypass a security feature locally.
ACTIVELY EXPLOITED IN THE WILD
This vulnerability is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.
Microsoft Office Security Feature Bypass Vulnerability
Microsoft Office
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
1/26/2026
Please adhere to Microsoft’s recommended guidelines to address this vulnerability. Implement all final mitigations provided by the vendor for Office 2021, and apply the interim corresponding mitigations for Office 2016 and Office 2019 until the final patch becomes available. For more information please see: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21509 ; https://nvd.nist.gov/vuln/detail/CVE-2026-21509
Vulnerability Summary
CVSS v3 Score
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS Score (Exploitation Probability)
This vulnerability has a 15.29% probability of being exploited in the next 30 days, ranking higher than 95% of all scored CVEs.
CWE Classification
Related Vulnerabilities
Same Weakness Type(CWE-807)
Reliance on untrusted inputs in a security decision in Microsoft Office Word allows an unauthorized attacker to bypass a security feature locally.
Conjur provides secrets management and application identity for infrastructure. Conjur OSS versions 1.19.5 through 1.22.0 and Secrets Manager, Self-Hosted (formerly known as Conjur Enterprise) 13.1 through 13.5 and 13.6 are vulnerable to bypass of the IAM authenticator. An attacker who can manipulate the headers signed by AWS can take advantage of a malformed regular expression to redirect the authentication validation request that Secrets Manager, Self-Hosted sends to AWS to a malicious server controlled by the attacker. This redirection could result in a bypass of the Secrets Manager, Self-Hosted IAM Authenticator, granting the attacker the permissions granted to the client whose request was manipulated. This issue affects both Secrets Manager, Self-Hosted (formerly Conjur Enterprise) and Conjur OSS. Conjur OSS version 1.22.1 and Secrets Manager, Self-Hosted versions 13.5.1 and 13.6.1 fix the issue.
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