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Object injection in PHPMailer/PHPMailer

Critical severity GitHub Reviewed Published Apr 29, 2021 in PHPMailer/PHPMailer • Updated Feb 7, 2024

Package

composer phpmailer/phpmailer (Composer)

Affected versions

>= 6.1.8, < 6.4.1

Patched versions

6.4.1

Description

Impact

This is a reintroduction of an earlier issue (CVE-2018-19296) by an unrelated bug fix in PHPMailer 6.1.8. An external file may be unexpectedly executable if it is used as a path to an attachment file via PHP's support for .phar files`. Exploitation requires that an attacker is able to provide an unfiltered path to a file to attach, or to trick calling code into generating one. See this article for more info.

Patches

This issue was patched in the PHPMailer 6.4.1 release. This release also implements stricter filtering for attachment paths; paths that look like any kind of URL are rejected.

Workarounds

Validate paths to loaded files using the same pattern as used in isPermittedPath() before using them in any PHP file function, such as file_exists. This method can't be used directly because it is protected, but you can implement the same thing in calling code. Note that this should be applied to all user-supplied paths passed into such functions; it's not a problem specific to PHPMailer.

Credit

This issue was found by Fariskhi Vidyan, reported and managed via Tidelift.

References

Published by the National Vulnerability Database Apr 28, 2021
@Synchro Synchro published to PHPMailer/PHPMailer Apr 29, 2021
Reviewed Apr 30, 2021
Published to the GitHub Advisory Database May 4, 2021
Last updated Feb 7, 2024

Severity

Critical

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS score

0.748%
(81st percentile)

Weaknesses

CVE ID

CVE-2020-36326

GHSA ID

GHSA-m298-fh5c-jc66

Source code

No known source code
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