How severe is CVE-2026-42171?

CVE-2026-42171 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-42171 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-42171?

CVE-2026-42171 affects Nullsoft Nullsoft Scriptable Install System. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-42171?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

Does CVE-2026-42171 have an EU (EUVD) identifier?

Yes. CVE-2026-42171 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25637.

When was CVE-2026-42171 published?

CVE-2026-42171 was published on 2026-04-24 and last updated on 2026-06-17.

CVE-2026-42171

CVE-2026-42171 is a high-severity vulnerability in Nullsoft Nullsoft Scriptable Install System with a CVSS 3.x base score of 7.8. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-427.

Key facts

Severity: High (CVSS 3.x base score 7.8)
EPSS exploit prediction: 0% (11th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-25637
Weakness: CWE-427
Affected product: Nullsoft Nullsoft Scriptable Install System
Published: 2026-04-24
Last modified: 2026-06-17

Description

NSIS (Nullsoft Scriptable Install System) 3.06.1 before 3.12 sometimes uses the Low IL temp directory when executing as SYSTEM, allowing local attackers to gain privileges (if they can cause my_GetTempFileName to return 0, as shown in the references).

Frequently asked questions

What is CVE-2026-42171?: NSIS (Nullsoft Scriptable Install System) 3.06.1 before 3.12 sometimes uses the Low IL temp directory when executing as SYSTEM, allowing local attackers to gain privileges (if they can cause my_GetTempFileName to return 0, as shown in the references).
How severe is CVE-2026-42171?: CVE-2026-42171 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-42171 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (11th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42171?: CVE-2026-42171 affects Nullsoft Nullsoft Scriptable Install System. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-42171?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
Does CVE-2026-42171 have an EU (EUVD) identifier?: Yes. CVE-2026-42171 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-25637.
When was CVE-2026-42171 published?: CVE-2026-42171 was published on 2026-04-24 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:nullsoft:nullsoft_scriptable_install_system:*:*:*:*:*:*:*:*

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