CVE-2025-15556: Notepad++ Notepad++

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

Yes, if you run Notepad++ Notepad++. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-02-12, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-03-05; treat that as the outer limit, not the target.
EPSS 1.8%, percentile 78: FIRST’s model estimates a 1.8% chance of exploitation activity in the next 30 days, higher than 78% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
Editorial verdict: Check exposure. Notepad++ Updater Hijack: State Actor Served Bad Updates — Targeting was narrow (about a dozen machines in Kaspersky's telemetry), but any fleet that auto-updated Notepad++ between June and December 2025 should update to v8.9.1+ and check the published IoCs.

What it is

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.

CISA’s summary

Notepad++ when using the WinGUp updater, contains a download of code without integrity check vulnerability that could allow an attacker to intercept or redirect update traffic to download and execute an attacker-controlled installer. This could lead to arbitrary code execution with the privileges of the user.

Weakness type: CWE-494.

Product: Notepad++ Notepad++ · Assigned by: VulnCheck · Published: 2026-02-03

Affected and fixed versions

Vendor	Product	Affected versions (per CVE record)
notepad-plus-plus	notepad-plus-plus	< 8.8.9

Severity scores

Scored by	CVSS	Score	Vector
VulnCheck	4.0	7.7 High	`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`

Attack vector: network (remotely reachable)
Attack complexity: high (needs special conditions)
Attack requirements: none
Privileges required: none (no login)
User interaction: passive

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

CISA KEV: added 2026-02-12; federal due date 2026-03-05. Known ransomware use: Unknown.
CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA SSVC assessment: exploitation active, automatable no, technical impact total.
FIRST EPSS (model of 2026-10-21): 1.77% probability of exploitation activity in the next 30 days; percentile 78.

Timeline

2026-02-02 — erroneo.us brief: Notepad++ Updater Hijack: State Actor Served Bad Updates
2026-02-03 — CVE record published by VulnCheck
2026-02-12 — Added to CISA’s Known Exploited Vulnerabilities catalog
2026-03-05 — CISA remediation deadline for US federal agencies
2026-03-05 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Other references from the CVE record and advisory

vulncheck.com vulncheck.com
notepad-plus-plus.org notepad-plus-plus.org

All exploited Notepad++ vulnerabilities · Today’s Security Digest