What is CVE-2018-19296?

CVE-2018-19296 is a high-severity insecure deserialization vulnerability in phpmailer/phpmailer (composer), affecting versions >= 5.0.0, < 5.2.27. It is fixed in 5.2.27, 6.0.6. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.

How severe is CVE-2018-19296?

CVE-2018-19296 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of phpmailer/phpmailer are affected by CVE-2018-19296?

phpmailer/phpmailer (composer) versions >= 5.0.0, < 5.2.27 is affected.

Is there a fix for CVE-2018-19296?

Yes. CVE-2018-19296 is fixed in 5.2.27, 6.0.6. Upgrade to this version or later.

Is CVE-2018-19296 exploitable, and should I be worried?

Whether CVE-2018-19296 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2018-19296 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

How do I fix CVE-2018-19296?

Upgrade: phpmailer/phpmailer to 5.2.27 or later, phpmailer/phpmailer to 6.0.6 or later.

CVE-2018-19296 in phpmailer/phpmailer

Q: How severe is CVE-2018-19296?

CVE-2018-19296 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of phpmailer/phpmailer are affected by CVE-2018-19296?

phpmailer/phpmailer (composer) versions >= 5.0.0, < 5.2.27 is affected.

Q: Is there a fix for CVE-2018-19296?

Yes. CVE-2018-19296 is fixed in 5.2.27, 6.0.6. Upgrade to this version or later.

Q: Is CVE-2018-19296 exploitable, and should I be worried?

Whether CVE-2018-19296 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2018-19296 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2018-19296?

Upgrade: phpmailer/phpmailer to 5.2.27 or later, phpmailer/phpmailer to 6.0.6 or later.

Summary

Phar object injection in PHPMailer

PHPMailer versions prior to 6.0.6 and 5.2.27 are vulnerable to an object injection attack by passing phar:// paths into addAttachment() and other functions that may receive unfiltered local paths, possibly leading to RCE. See this article for more info on this type of vulnerability. Mitigated by blocking the use of paths containing URL-protocol style prefixes such as phar://. Reported by Sehun Oh of cyberone.kr.

Workarounds

Validate and sanitise user input before using.

References

https://nvd.nist.gov/vuln/detail/CVE-2018-19296

For more information

If you have any questions or comments about this advisory:

Open a private issue in the PHPMailer project

Impact

Object injection, possible remote code execution

Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect. Typical impact: arbitrary code execution or logic abuse.

CVE-2018-19296 has a CVSS score of 8.8 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.2.27, 6.0.6); upgrading removes the vulnerable code path.

Affected versions

phpmailer/phpmailer (>= 5.0.0, < 5.2.27) phpmailer/phpmailer (>= 6.0.0, < 6.0.6)

Security releases

phpmailer/phpmailer → 5.2.27 (composer) phpmailer/phpmailer → 6.0.6 (composer)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Fixed in 6.0.6 and 5.2.27

Frequently Asked Questions

What is CVE-2018-19296? CVE-2018-19296 is a high-severity insecure deserialization vulnerability in phpmailer/phpmailer (composer), affecting versions >= 5.0.0, < 5.2.27. It is fixed in 5.2.27, 6.0.6. Untrusted serialized data is processed by a deserializer that can instantiate arbitrary objects or execute code as a side effect.
How severe is CVE-2018-19296? CVE-2018-19296 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of phpmailer/phpmailer are affected by CVE-2018-19296? phpmailer/phpmailer (composer) versions >= 5.0.0, < 5.2.27 is affected.
Is there a fix for CVE-2018-19296? Yes. CVE-2018-19296 is fixed in 5.2.27, 6.0.6. Upgrade to this version or later.
Is CVE-2018-19296 exploitable, and should I be worried? Whether CVE-2018-19296 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2018-19296 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2018-19296?
- Upgrade phpmailer/phpmailer to 5.2.27 or later
- Upgrade phpmailer/phpmailer to 6.0.6 or later

Other vulnerabilities in phpmailer/phpmailer

CVE-IDSeverityPackage summary

CVE-2006-5734Mediumphpmailer/phpmailer: PHPMailer Local file inclusion CVE-2007-3215Highphpmailer/phpmailer: PHPMailer Shell command injection CVE-2012-0796Highphpmailer/phpmailer: PHPMailer vulnerable to email header injection CVE-2008-5619Highphpmailer/phpmailer: PHPMailer susceptible to arbitrary code execution CVE-2021-3603Highphpmailer/phpmailer: PHPMailer untrusted code may be run from an overridden address validator