Notepad++ Download of Code Without Integrity Check Vulnerability
Notepad++ · Notepad++
Notepad++ versions prior to 8.8.9 contain a flaw in the WinGUp updater, which does not cryptographically verify downloaded update metadata and installers. An attacker who can intercept or redirect update traffic can get the updater to download and run a malicious installer, achieving arbitrary code execution with the user's privileges, though this requires the attacker to control the update traffic path and the user to trigger or accept the update.
Notepad++ versions prior to 8.8.9, when using the WinGUp updater, contain an update integrity verification vulnerability where downloaded update metadata and installers are not cryptographically verified. An attacker able to intercept or redirect update traffic can cause the updater to download and execute an attacker-controlled installer, resulting in arbitrary code execution with the privileges of the user.
- Exploited
- Yes, in CISA KEV
- Reports
- 0
- Tactics
- 3/15
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 1 day before it was disclosed. Public exploit code (PoC-in-GitHub) appeared 6 days after disclosure.
- First seen exploitedVulnCheck KEV evidence1 day before
- Disclosedday 0
- Public exploit codePoC-in-GitHub+6 days
- Added to CISA KEVEU database agrees+9 days
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 2ExecutionTA0002
Updater executes attacker-supplied installer, user-context execution
cause the updater to download and execute an attacker-controlled installer
Credential AccessTA0006
Intercepting update traffic enables the initial compromise path
An attacker able to intercept or redirect update traffic
Detection
0 rules for this CVE · 49 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-2025-15556 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.
Adversary-in-the-MiddleT155710 general rules
- Suspicious Child Process of Notepad++ Updater - GUP.Exehighexperimental
- Uncommon File Created by Notepad++ Updater Gup.EXEhighexperimental
- Potential Suspicious Activity Using SeCEditmediumtest
- ISATAP Router Address Was Setmediumexperimental
- Notepad++ Updater DNS Query to Uncommon Domainsmediumexperimental
- Cisco BGP Authentication Failureslowtest
- Cisco LDP Authentication Failureslowtest
- Huawei BGP Authentication Failureslowtest
Malicious FileT1204.00239 general rules
- Droppers Exploiting CVE-2017-11882criticalstable
- Ursnif Malware C2 URL Patterncriticalstable
- Exploit for CVE-2017-8759criticaltest
- Potential Maze Ransomware Activitycriticaltest
- File With Uncommon Extension Created By An Office Applicationhightest
- Flash Player Update from Suspicious Locationhightest
- GAC DLL Loaded Via Office Applicationshightest
- HackTool - LittleCorporal Generated Maldoc Injectionhightest
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 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
- Actively_Exploited_Kev | Oct 23, 202622 Oct 2026
- 44 more on OTX