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Vulnerability details: VCID-377c-stcv-abgs
Vulnerability ID VCID-377c-stcv-abgs
Aliases CVE-2021-3603
GHSA-77mr-wc79-m8j3
Summary PHPMailer 6.4.1 and earlier contain a vulnerability that can result in untrusted code being called (if such code is injected into the host project's scope by other means). If the $patternselect parameter to validateAddress() is set to 'php' (the default, defined by PHPMailer::$validator), and the global namespace contains a function called php, it will be called in preference to the built-in validator of the same name. Mitigated in PHPMailer 6.5.0 by denying the use of simple strings as validator function names.
Status Published
Exploitability 0.5
Weighted Severity 8.0
Risk 4.0
Affected and Fixed Packages Package Details
Weaknesses (4)
CWE-74 Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')
CWE-829 Inclusion of Functionality from Untrusted Control Sphere
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
epss 0.00278 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00279 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00279 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00487 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00488 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
epss 0.00488 https://api.first.org/data/v1/epss?cve=CVE-2021-3603
cvssv3.1_qr HIGH https://github.com/advisories/GHSA-77mr-wc79-m8j3
cvssv3.1 8.1 https://github.com/FriendsOfPHP/security-advisories/blob/master/phpmailer/phpmailer/CVE-2021-3603.yaml
generic_textual HIGH https://github.com/FriendsOfPHP/security-advisories/blob/master/phpmailer/phpmailer/CVE-2021-3603.yaml
cvssv3.1 8.1 https://github.com/PHPMailer/PHPMailer
generic_textual HIGH https://github.com/PHPMailer/PHPMailer
cvssv3.1 8.1 https://github.com/PHPMailer/PHPMailer/commit/45f3c18dc6a2de1cb1bf49b9b249a9ee36a5f7f3
generic_textual HIGH https://github.com/PHPMailer/PHPMailer/commit/45f3c18dc6a2de1cb1bf49b9b249a9ee36a5f7f3
cvssv3.1 8.1 https://github.com/PHPMailer/PHPMailer/releases/tag/v6.5.0
generic_textual HIGH https://github.com/PHPMailer/PHPMailer/releases/tag/v6.5.0
cvssv3.1 8.1 https://github.com/PHPMailer/PHPMailer/security/advisories/GHSA-77mr-wc79-m8j3
cvssv3.1_qr HIGH https://github.com/PHPMailer/PHPMailer/security/advisories/GHSA-77mr-wc79-m8j3
generic_textual HIGH https://github.com/PHPMailer/PHPMailer/security/advisories/GHSA-77mr-wc79-m8j3
cvssv3.1 8.1 https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3YRMWGA4VTMXFB22KICMB7YMFZNFV3EJ
generic_textual HIGH https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3YRMWGA4VTMXFB22KICMB7YMFZNFV3EJ
cvssv3.1 8.1 https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FJYSOFCUBS67J3TKR74SD3C454N7VTYM
generic_textual HIGH https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FJYSOFCUBS67J3TKR74SD3C454N7VTYM
cvssv2 6.8 https://nvd.nist.gov/vuln/detail/CVE-2021-3603
cvssv3.1 8.1 https://nvd.nist.gov/vuln/detail/CVE-2021-3603
generic_textual HIGH https://nvd.nist.gov/vuln/detail/CVE-2021-3603
cvssv3.1 8.1 https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-3603
generic_textual HIGH https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-3603
cvssv3.1 8.1 https://www.huntr.dev/bounties/1-PHPMailer/PHPMailer
generic_textual HIGH https://www.huntr.dev/bounties/1-PHPMailer/PHPMailer
Reference id Reference type URL
https://api.first.org/data/v1/epss?cve=CVE-2021-3603
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-3603
https://github.com/FriendsOfPHP/security-advisories/blob/master/phpmailer/phpmailer/CVE-2021-3603.yaml
https://github.com/PHPMailer/PHPMailer
https://github.com/PHPMailer/PHPMailer/commit/45f3c18dc6a2de1cb1bf49b9b249a9ee36a5f7f3
https://github.com/PHPMailer/PHPMailer/releases/tag/v6.5.0
https://github.com/PHPMailer/PHPMailer/security/advisories/GHSA-77mr-wc79-m8j3
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3YRMWGA4VTMXFB22KICMB7YMFZNFV3EJ
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3YRMWGA4VTMXFB22KICMB7YMFZNFV3EJ/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FJYSOFCUBS67J3TKR74SD3C454N7VTYM
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FJYSOFCUBS67J3TKR74SD3C454N7VTYM/
https://nvd.nist.gov/vuln/detail/CVE-2021-3603
https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-3603
https://www.huntr.dev/bounties/1-PHPMailer/PHPMailer
https://www.huntr.dev/bounties/1-PHPMailer/PHPMailer/
991666 https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=991666
cpe:2.3:a:phpmailer_project:phpmailer:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:phpmailer_project:phpmailer:*:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*
GHSA-77mr-wc79-m8j3 https://github.com/advisories/GHSA-77mr-wc79-m8j3
USN-5956-1 https://usn.ubuntu.com/5956-1/
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://github.com/FriendsOfPHP/security-advisories/blob/master/phpmailer/phpmailer/CVE-2021-3603.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://github.com/PHPMailer/PHPMailer
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://github.com/PHPMailer/PHPMailer/commit/45f3c18dc6a2de1cb1bf49b9b249a9ee36a5f7f3
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://github.com/PHPMailer/PHPMailer/releases/tag/v6.5.0
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://github.com/PHPMailer/PHPMailer/security/advisories/GHSA-77mr-wc79-m8j3
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3YRMWGA4VTMXFB22KICMB7YMFZNFV3EJ
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FJYSOFCUBS67J3TKR74SD3C454N7VTYM
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: AV:N/AC:M/Au:N/C:P/I:P/A:P Found at https://nvd.nist.gov/vuln/detail/CVE-2021-3603
Exploitability (E) Access Vector (AV) Access Complexity (AC) Authentication (Au) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

high

functional

unproven

proof_of_concept

not_defined

local

adjacent_network

network

high

medium

low

multiple

single

none

none

partial

complete

none

partial

complete

none

partial

complete
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://nvd.nist.gov/vuln/detail/CVE-2021-3603
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2021-3603
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H Found at https://www.huntr.dev/bounties/1-PHPMailer/PHPMailer
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.51062
EPSS Score 0.00278
Published At Aug. 3, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:41:19.858205+00:00 Ubuntu USN Importer Import https://usn.ubuntu.com/5956-1/ 37.0.0