CVE-2026-40947

Local code execution via unrestricted DLL loading

Published Apr 15, 2026 · Updated Apr 15, 2026

DLL search-path hijacking in Yubico libfido2, python-fido2, and YubiKey Manager allows local users to execute code on Windows. libfido2 before 1.17.0 calls LoadLibrary without limiting resolution to System32; python-fido2 before 2.2.0 and YubiKey Manager before 5.9.1 likewise call WinDLL without the restrictive search-mode flag. The attacker must write into the software or Python installation directory, which requires Administrator access when that directory is protected.

CVSS severity2.9
Low
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

DLL search-path hijacking in Yubico libfido2, python-fido2, and YubiKey Manager allows local users to execute code on Windows. libfido2 before 1.17.0 calls LoadLibrary without limiting resolution to System32; python-fido2 before 2.2.0 and YubiKey Manager before 5.9.1 likewise call WinDLL without the restrictive search-mode flag. The attacker must write into the software or Python installation directory, which requires Administrator access when that directory is protected.

The record

CVE
CVE-2026-40947
Published
Apr 15, 2026
Updated
Apr 15, 2026
Vendor
Yubico
Product
YubiKey Manager CLI
Classifications
CWE-426, T1574.001
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 15, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 15, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <5.9.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Yubico · YubiKey Manager CLIversion=0 <5.9.1
Yubico · python-fido2version=0 <2.2.0
Yubico · libfido2version=0 <1.17.0

Published CVSS scores

2.9MITRECVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-426Untrusted Search Path
T1574.001DLL Search Order Hijacking

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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