How severe is CVE-2026-42897?

CVE-2026-42897 has a CVSS score of 8.1/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2026-42897?

Affected package information for CVE-2026-42897 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2026-42897?

No fixed version has been published for CVE-2026-42897 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2026-42897 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2026-42897, including . All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2026-42897?

CVE-2026-42897 has an EPSS (Exploit Prediction Scoring System) score of 7.9%, placing it in the 92th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

Is CVE-2026-42897 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2026-42897 (Microsoft Exchange Server Cross-Site Scripting Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-05-15. CISA required all US federal civilian agencies to remediate this vulnerability by 2026-05-29. The required action was: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2026-42897?

CVE-2026-42897 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

Which products and versions are affected by CVE-2026-42897?

CVE-2026-42897 affects microsoft exchange server (2 versions, e.g. 2016, 2019). Check the affected-products list on this page against your deployed version to confirm exposure.

When was CVE-2026-42897 published, and has it been updated?

CVE-2026-42897 was published on May 14, 2026 and was last updated on May 15, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2026-05-15 — agencies required to remediate by 2026-05-29

CVE-2026-42897

HIGH

Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

Published

May 14, 2026

Updated

May 15, 2026

Affected

0 pkgs

Patched

None yet

Exploits

1 known

EPSS Exploitation Probability

via FIRST.org ↗

7.9%probability of exploitation in next 30 days

Lower Risk92th percentile-2.87%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Description

Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

Affected Products

1 product · 40 configurations

Application

exchange servermicrosoft

2 versions

20162019

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

atiilla/CVE-2026-42897

CVE-2026-42897 - Exchange Health Checker blind spot: outbound IIS URL Re

⭐ 4🍴 3Jun 2026

Frequently Asked Questions

Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Exchange Server allows an unauthorized attacker to perform spoofing over a network.

O3 Security · Impact-Aware SCA

Is CVE-2026-42897 in your stack?

O3 detects CVE-2026-42897 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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