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Fencer Vulns
medium 6.3

CVE-2026-52885 json

Notepad++ TOCTOU: HMAC Checks Disk, Executes from Memory

published 2026-06-26 4 mo ago modified 2026-06-29 4 mo ago also EUVD-2026-39906

cvss
6.3
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

Summary

Notepad++ is a free and open-source source code editor. Prior to 8.9.6.4, NppCommands.cpp checks the HMAC of the on-disk shortcuts.xml at the moment a user command fires (Time-of-Check). However, the command payload is taken from the in-memory _userCommands vector, which is populated at application startup and never re-synchronized with the on-disk file (Time-of-Use). Swapping shortcuts.xml between startup and command execution causes the HMAC check to validate a clean file while a malicious command runs. An attacker with write access to shortcuts.xml places a malicious version on disk before launch, then immediately restores the legitimate file. The HMAC check at execution time validates the restored legitimate file (check passes), while the malicious payload executes from memory. This vulnerability is fixed in 8.9.6.4.

Patch / fix

  • notepad-plus-plus notepad++ 8.9.6.4

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
4 mo ago

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/notepad-plus-plus/notepad-plus-plus/security/advisories/GHSA-qm4c-qg8p-qfcr referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 7.5 CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA 4.0 7.5 CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 6.3 CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:H/A:H

Affected products

  • notepad-plus-plus notepad-plus-plus

Classification

Weakness
  • CWE-367 Time-of-check Time-of-use (TOCTOU) Race Condition

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.