NVD / CVE Program· CNA GitHub_M

CVE-2023-40031: Notepad++ vulnerable to heap buffer write overflow in Utf8_16_Read::convert

Noroxi assessment

Priority: Monitor (action score 31/100)

Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
Probability of exploitation in the next 30 days: 0.51% (FIRST EPSS).
Someone with local access to the system can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
According to the record, no fixed version is available yet.

Low priority for now. Update when a fix is released; follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Notepad++ is a free and open-source source code editor. Versions 8.5.6 and prior are vulnerable to heap buffer write overflow in `Utf8_16_Read::convert`. This issue may lead to arbitrary code execution. As of time of publication, no known patches are available in existing versions of Notepad++.

HighCVSS 7.8 · v3.1—Proof of concept No fix recorded

BDU:2023-05051

Published: Aug 25, 2023
Updated: Jun 17, 2026
EPSS: 0.5% · 44th percentile
CWE: CWE-120

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 31 / 40 · 7.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.5%

CISA SSVC decision

Exploitation: proof of concept
Automatable: no
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 7.8
CNA · GitHub_M: 7.8; agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
Proof of concept exists, no weaponized module
No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
notepad-plus-plus	notepad\+\+	cpe:2.3:a:notepad-plus-plus:notepad\+\+

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

notepad-plus-plus notepad++up to 8.5.6 inclusive

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

notepad-plus-plus notepad-plus-plus
- <= 8.5.6affected

Same product

notepad-plus-plus: all records

Other highest-scoring records for the same primary product.

CVE-2025-15556Notepad++ < 8.8.9 WinGUp Updater Lacks Update Integrity VerificationKEV
61This week
CVE-2026-52884Notepad++: CVE-2026-48800 Bypass
31Monitor
CVE-2026-48800Notepad++: Arbitrary Code Execution via shortcuts.xml UserCommand Injection
31Monitor

Published before and after this one in the same product

← EarlierCVE-2022-31901Jan 19, 2023 · Buffer overflow in function Notepad_plus::addHotSpot in Notepad++ v8.4.3 and earlier allows attackers to crash the application via two craft
26Monitor
← EarlierCVE-2022-31902Jan 31, 2023 · Notepad++ v8.4.1 was discovered to contain a stack overflow via the component Finder::add().
22Monitor
Later →CVE-2023-40036Aug 25, 2023 · Notepad++ global buffer read overflow in CharDistributionAnalysis::HandleOneChar
22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

Proof-of-concept repository on GitHub ×1

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
Source	Kind	Date
Proof-of-concept repository on GitHub	stars:15	2023-09-08

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

PublishedAug 25, 2023
First PoCSep 8, 2023+13 d
TodayNov 10, 2026+1173 d

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Someone with local access to the system can trigger it.
No account or password is required.
A user must open a link or visit a page.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Local
Attack complexity: Low
Privileges required: None
User interaction: Required
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: High

Weakness class (CWE)

CWE-120 · Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

nvd-primary

Root cause

When data is copied, the source length is not compared with the size of the destination buffer. Excess data overwrites adjacent memory.

The bug in code

The whole CWE-120 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1char buf[256];
2memcpy(buf, pkt->data, pkt->len);

Fixed

1char buf[256];
2if (pkt->len > sizeof(buf)) {
3  return -EINVAL;
4}
5memcpy(buf, pkt->data, pkt->len);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

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Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

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