Cyber Resilience

CVE-2026-5525

Memory Safety in Notepad-Plus-Plus Notepad\+\+ 8.9.3

Public PoCMemory Safety
Published
10 April 2026
Modified
05 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 6.0
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:N
EPSS Score 0.0017 6th percentile
Risk Priority 40 floored blend · peak EPSS

Summary

CVE-2026-5525 is a medium-severity Stack-based Buffer Overflow (CWE-121) vulnerability in Notepad-Plus-Plus Notepad\+\+. Its CVSS base score is 6.0 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 6th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SI-10 (Information Input Validation) and SI-16 (Memory Protection) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

A stack-based buffer overflow vulnerability exists in Notepad++ version 8.9.3 in the file drop handler component. When a user drags and drops a directory path of exactly 259 characters without a trailing backslash, the application appends a backslash and null…

more

terminator without proper bounds checking, resulting in a stack buffer overflow and application crash (STATUS_STACK_BUFFER_OVERRUN).

CWE(s)
CWE-121

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
Why these techniques?

Stack buffer overflow leads directly to application crash, enabling endpoint DoS via exploitation of client-side software.

Confidence: MEDIUM · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2025-15556Same product: Notepad-Plus-Plus Notepad\+\+
CVE-2026-48770Same product: Notepad-Plus-Plus Notepad\+\+
CVE-2023-40166Same product: Notepad-Plus-Plus Notepad\+\+
CVE-2026-52884Same product: Notepad-Plus-Plus Notepad\+\+
CVE-2023-40164Same product: Notepad-Plus-Plus Notepad\+\+
CVE-2026-48800Same product: Notepad-Plus-Plus Notepad\+\+
CVE-2023-40031Same product: Notepad-Plus-Plus Notepad\+\+
CVE-2026-52885Same product: Notepad-Plus-Plus Notepad\+\+
CVE-2026-46710Same product: Notepad-Plus-Plus Notepad\+\+
CVE-2026-25926Same product: Notepad-Plus-Plus Notepad\+\+

Affected Assets

notepad-plus-plus
notepad\+\+
8.9.3

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)
  • SI-10 Information Input Validation
  • SI-16 Memory Protection
Detect
Catch it (NIST detect / respond)
  • SI-2 Flaw Remediation
Harden
Shrink the surface (DISA STIG)
  • 2 hardening rules · 2 OS baselines
Validate
Prove the fix (OWASP ASVS)

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Mitigating Controls (NIST 800-53 r5) AI

SI-10 Information Input Validation good match
prevent

Directly enforces bounds and format checks on untrusted path strings supplied via drag-and-drop, preventing the 259-character overflow in the file-drop handler.

SI-16 Memory Protection good match
prevent

Applies OS-level memory protections (ASLR, DEP, stack canaries) that detect and terminate the process on the stack-buffer overrun before code execution.

SI-2 Flaw Remediation partial match
respondrecover

Requires prompt application of vendor patches that correct the missing length check when appending the backslash in the drop handler.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure-development practices directly prevent introduction of stack buffer overflows.

ID.RA-01 partial match
prevents

Vulnerability scanning can discover stack buffer overflows but does not prevent their introduction.

PR.PS-02 partial match
prevents

Patching eliminates known instances of the weakness after discovery.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
detects

Security testing (fuzzing, static analysis) detects stack overflows before release.

A.8.25 Secure development life cycle partial match
prevents

Secure SDLC mandates buffer-safety practices that directly prevent stack overflows.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify buffer-size and input-validation rules.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture principles include memory-safety and least-privilege stack usage.

A.8.28 Secure coding partial match
prevents

Secure coding standards explicitly forbid unsafe buffer handling that causes CWE-121.

A.8.32 Change management none match
none

Change-management gates can enforce security reviews that catch buffer issues.

References