What is CVE-2025-15556?
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.
The record classifies CVE-2025-15556 under weakness class CWE-494. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 244 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 7.5 — HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H - CVSS v4.0 base score
- 7.7
- EPSS (FIRST)
- 5.3% probability of exploitation in the next 30 days, higher than 90.0% of all scored CVEs
- CISA KEV
- Listed since 2026-02-12, federal remediation deadline 2026-03-05
- Threadlinqs priority
- 9/10 — CISA KEV-listed, which Threadlinqs floors at 9
- Published
- 2026-02-03, last modified 2026-02-13
Is CVE-2025-15556 being exploited?
CISA added CVE-2025-15556 to the Known Exploited Vulnerabilities catalog on 2026-02-12, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-03-05 under BOD 22-01. It currently carries a trending score of 38 in the Threadlinqs vulnerability feed.
Affected products and versions
- Notepad-plus-plus: Notepad++
How to fix CVE-2025-15556
The record marks a vendor fix as available for CVE-2025-15556. Vendor advisory: https://github.com/notepad-plus-plus/notepad-plus-plus/commit/bcf2aa68ef414338d717e20e059459570ed6c5ab. Because CVE-2025-15556 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-03-05. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2025-15556
1 tracked threat in the Threadlinqs corpus references CVE-2025-15556, either in the campaign’s CVE list or as an indicator on the campaign record.
- Lotus Blossom APT Supply Chain Compromise of Notepad++ Update Infrastructure (CVE-2025-15556) — CRITICAL · 2026-03-12
Sources
Seeded from threadlinqs-intel and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.