Microsoft Exchange Server Cross-Site Scripting Vulnerability
Microsoft · Microsoft
Microsoft Exchange Server contains a cross-site scripting flaw caused by improper neutralization of input during web page generation. An unauthenticated attacker over the network can perform spoofing against users, and exploitation requires that a user interact with a crafted element, such as by visiting a malicious page or link.
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.
- Exploited
- Yes, in CISA KEV
- Reports
- 0
- Tactics
- 2/15
How an attack unfolds
Based on MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. mappings. Select a step to see the evidence.How attackers get in
What they do
Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited the day it was disclosed. Public exploit code (PoC-in-GitHub) appeared 1 day after disclosure.
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
2 TechniqueOne specific attacker behaviour in MITRE ATT&CK, such as T1190 “Exploit Public-Facing Application”. IDs with a dot, like T1059.004, are sub-techniques., grouped by TacticThe attacker’s goal at a stage of an attack in MITRE ATT&CK, such as Initial Access or Persistence. Each technique belongs to one or more tactics. in kill-chain order, 2 cited passages 2Initial AccessTA0001
XSS delivered via user-visited web content
Improper neutralization of input during web page generation ('cross-site scripting')
ExecutionTA0002
Spoofing via injected script in web page
allows an unauthorized attacker to perform spoofing over a network
Detection
0 rules for this CVE · 32 general rules for its techniquesRules for this CVE
0Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2026-42897 directly.CVE-specific rules are not available in this build. Search SigmaHQ ↗
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
Drive-by CompromiseT11893 general rules
JavaScriptT1059.00729 general rules
- Adwind RAT / JRAThightest
- Adwind RAT / JRAT File Artifacthightest
- Csc.EXE Execution Form Potentially Suspicious Parenthightest
- Cscript/Wscript Uncommon Script Extension Executionhightest
- HackTool - CACTUSTORCH Remote Thread Creationhightest
- HackTool - Koadic Executionhightest
- HTML Help HH.EXE Suspicious Child Processhightest
- JXA In-memory Execution Via OSAScripthightest
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Not named in any threat report yetAlso mentioned in 50 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Actively_Exploited_Kev | Oct 31, 202630 Oct 2026
- Actively_Exploited_Kev | Oct 30, 202629 Oct 2026
- Actively_Exploited_Kev | Oct 29, 202628 Oct 2026
- Actively_Exploited_Kev | Oct 28, 202627 Oct 2026
- Actively_Exploited_Kev | Oct 27, 202626 Oct 2026
- Actively_Exploited_Kev | Oct 24, 202623 Oct 2026
- 44 more on OTX