How severe is CVE-2021-34551?

CVE-2021-34551 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-34551 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-34551?

CVE-2021-34551 primarily affects Phpmailer Project Phpmailer. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-34551?

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.

When was CVE-2021-34551 published?

CVE-2021-34551 was published on 2021-06-16 and last updated on 2026-06-17.

CVE-2021-34551

CVE-2021-34551 is a high-severity vulnerability in Phpmailer Project Phpmailer with a CVSS 3.x base score of 8.1. 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-434.

Key facts

Severity: High (CVSS 3.x base score 8.1)
CVSS v2: 5.1
EPSS exploit prediction: 3% (85th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-434
Affected product: Phpmailer Project Phpmailer
Published: 2021-06-16
Last modified: 2026-06-17

Description

PHPMailer before 6.5.0 on Windows allows remote code execution if lang_path is untrusted data and has a UNC pathname.

Frequently asked questions

What is CVE-2021-34551?: PHPMailer before 6.5.0 on Windows allows remote code execution if lang_path is untrusted data and has a UNC pathname.
How severe is CVE-2021-34551?: CVE-2021-34551 has a CVSS 3.x base score of 8.1, rated high severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-34551 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 3% (85th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-34551?: CVE-2021-34551 primarily affects Phpmailer Project Phpmailer. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-34551?: 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.
When was CVE-2021-34551 published?: CVE-2021-34551 was published on 2021-06-16 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:phpmailer_project:phpmailer:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

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