How severe is CVE-2018-20340?

CVE-2018-20340 has a CVSS 3.x base score of 6.8, rated medium severity. It is exploitable over physical access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2018-20340 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2018-20340?

CVE-2018-20340 primarily affects Yubico Libu2f-host. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2018-20340?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2018-20340 published?

CVE-2018-20340 was published on 2019-03-21 and last updated on 2026-06-17.

CVE-2018-20340

CVE-2018-20340 is a medium-severity vulnerability in Yubico Libu2f-host with a CVSS 3.x base score of 6.8. 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-119.

Key facts

Severity: Medium (CVSS 3.x base score 6.8)
CVSS v2: 4.6
EPSS exploit prediction: 0% (39th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-119
Affected product: Yubico Libu2f-host
Published: 2019-03-21
Last modified: 2026-06-17

Description

Yubico libu2f-host 1.1.6 contains unchecked buffers in devs.c, which could enable a malicious token to exploit a buffer overflow. An attacker could use this to attempt to execute malicious code using a crafted USB device masquerading as a security token on a computer where the affected library is currently in use. It is not possible to perform this attack with a genuine YubiKey.

Frequently asked questions

What is CVE-2018-20340?: Yubico libu2f-host 1.1.6 contains unchecked buffers in devs.c, which could enable a malicious token to exploit a buffer overflow. An attacker could use this to attempt to execute malicious code using a crafted USB device masquerading as a security token on a computer where the affected library is currently in use. It is not possible to perform this attack with a genuine YubiKey.
How severe is CVE-2018-20340?: CVE-2018-20340 has a CVSS 3.x base score of 6.8, rated medium severity. It is exploitable over physical access with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2018-20340 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (39th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2018-20340?: CVE-2018-20340 primarily affects Yubico Libu2f-host. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2018-20340?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2018-20340 published?: CVE-2018-20340 was published on 2019-03-21 and last updated on 2026-06-17.

References

Affected products (2)

cpe:2.3:a:yubico:libu2f-host:1.1.6:*:*:*:*:*:*:*
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

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