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CVE-2021-34551

25
FAUCET Score

CVE-2021-34551 describes a remote code execution vulnerability in PHPMailer versions prior to 6.5.0, specifically impacting Windows environments when the lang_path parameter contains untrusted data and a UNC pathname. This high-severity flaw (CVSS 8.1) could allow an unauthenticated attacker to achieve full compromise of confidentiality, integrity, and availability with high attack complexity. While there is no evidence of active exploitation, public exploit code, or KEV listing, the vulnerability has garnered some community discussion and media coverage, indicating awareness within the cybersecurity landscape.

Impacted Technologies

VendorProductVersion(s)CPE
< 6.5.0CPE matchmatch criteria
cpe:2.3:a:phpmailer_project:phpmailer:*:*:*:*:*:*:*:*
33CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
34CPE matchmatch criteria
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

8.1HIGH

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.2
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
2.80%
Probability of exploitation in next 30 days
EPSS Percentile
85.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0280 is in the 43rd percentile among its peer group of 8,920 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.2 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

composerpatch availablevia ghsa
Product: phpmailer/phpmailerFixed in: 6.5.0

Vendor Advisories (1)

composerGHSA-7q44-r25x-wm4qhigh

Remote Code Execution vulnerability in PHPMailer 6.4.1 running on Windows

Jun 22, 2021

References

github.com / PHPMailer/PHPMailer/blob/master/SECURITY.md
Issue TrackingThird Party Advisory
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/3YRMWGA4VTMXFB22KICMB7YMFZNFV3EJ
lists.fedoraproject.org / archives/list/package-announce%40lists.fedoraproject.org/message/FJYSOFCUBS67J3TKR74SD3C454N7VTYM