What’s Vulnerable › Vulnerabilities

CVE-2019-3556

• Severity: high (CVSS 8.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2021-10-26 · updated 2026-06-17
• Weakness: CWE-22

Description

HHVM supports the use of an "admin" server which accepts administrative requests over HTTP. One of those request handlers, dump-pcre-cache, can be used to output cached regular expressions from the current execution context into a file. The handler takes a parameter which specifies where on the filesystem to write this data. The parameter is not validated, allowing a malicious user to overwrite arbitrary files where the user running HHVM has write access. This issue affects HHVM versions prior to 4.56.2, all versions between 4.57.0 and 4.78.0, as well as 4.79.0, 4.80.0, 4.81.0, 4.82.0, and 4.83.0.

Affected products

• Facebook HHVM: before 4.56.2; from 4.57.0 through 4.78.0; 4.79.0, 4.80.0, 4.81.0, 4.82.0, 4.83.0 — fixed in 4.56.2

How to fix

Upgrade to a fixed version: Facebook HHVM 4.56.2. Check the vendor advisory for mitigations.

References

• https://github.com/facebook/hhvm/commit/abe0b29e4d3a610f9bc920b8be4ad8403364c2d4
• https://hhvm.com/blog/2020/11/12/security-update.html
• https://www.facebook.com/security/advisories/cve-2019-3556
• https://github.com/facebook/hhvm/commit/abe0b29e4d3a610f9bc920b8be4ad8403364c2d4
• https://hhvm.com/blog/2020/11/12/security-update.html
• https://www.facebook.com/security/advisories/cve-2019-3556

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