CVE-2017-11503: PHPMailer 5.2.23 has XSS in the "From Email Address" and "To Email Address" fields of code_generator.php.

This month

MEDIUM 6.1DOWNGRADE

CVE-2017-11503 is a medium-severity flaw (CVSS 6.1) affecting phpmailer. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

PHPMailer 5.2.23 has XSS in the "From Email Address" and "To Email Address" fields of code_generator.php.

Why this priority

Public exploit reference

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	2.4% (top 16%)
CISA exploited list	No
Weakness	CWE-79
Published	2017-07-20
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: phpmailer project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2017-07-20 23:29 UTCPublished CVE record published
2026-06-17 01:01 UTCUpdated Record last modified

phpmailer project phpmailer DOWNGRADE

Affected: 5.2.23

Fixed in: no fixed release known

Safe to downgrade to: a release before 5.2.23

1. Check installed version

apt-cache policy phpmailer || rpm -q phpmailer || phpmailer --version

2. No fixed release: DOWNGRADE to a release before 5.2.23 (Debian / Ubuntu)

apt-cache madison phpmailer sudo apt install phpmailer=<VERSION_BEFORE_5.2.23> sudo apt-mark hold phpmailer

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list phpmailer sudo dnf downgrade phpmailer-<VERSION_BEFORE_5.2.23> sudo dnf versionlock add phpmailer

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2017-11503?

phpmailer: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2017-11503 being exploited?

CVE-2017-11503 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2017-11503 affect?

CVE-2017-11503 affects phpmailer. Severity is medium (CVSS 6.1). PHPMailer 5.2.23 has XSS in the "From Email Address" and "To Email Address" fields of code_generator.php.

How urgent is CVE-2017-11503?

Priority 47/100. Public exploit reference

Software pages

PHP vulnerabilities

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References

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