CVE-2021-24025

Name: CVE-2021-24025
Creator: NVD / NIST
Published: 2021-03-10T16:15:16.75+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.66%

Last modified Jun 17, 2026

CVE-2021-24025 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. Due to incorrect string size calculations inside the preg_quote function, a large input string passed to the function can trigger an integer overflow leading to a heap overflow. This issue affects HHVM versions prior to 4.56.3, all versions between 4.57.0 and 4.80.1, all versions between 4.81.0 and 4.93.1, and versions 4.94.0, 4.95.0, 4.96.0, 4.97.0, 4.98.0.. EPSS estimates a 1.66% chance of exploitation in the next 30 days.

Description

Due to incorrect string size calculations inside the preg_quote function, a large input string passed to the function can trigger an integer overflow leading to a heap overflow. This issue affects HHVM versions prior to 4.56.3, all versions between 4.57.0 and 4.80.1, all versions between 4.81.0 and 4.93.1, and versions 4.94.0, 4.95.0, 4.96.0, 4.97.0, 4.98.0.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.66%

73.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Facebook	Hhvm	< 4.56.3
Facebook	Hhvm	>= 4.57.0, <= 4.80.1
Facebook	Hhvm	>= 4.81.0, <= 4.93.1
Facebook	Hhvm	4.94.0
Facebook	Hhvm	4.95.0
Facebook	Hhvm	4.96.0
Facebook	Hhvm	4.97.0
Facebook	Hhvm	4.98.0

References

https://github.com/facebook/hhvm/commit/08193b7f0cd3910256e00d599f0f3eb2519c44caPatch, Third Party Advisory
https://hhvm.com/blog/2021/02/25/security-update.htmlRelease Notes, Third Party Advisory
https://github.com/facebook/hhvm/commit/08193b7f0cd3910256e00d599f0f3eb2519c44caPatch, Third Party Advisory
https://hhvm.com/blog/2021/02/25/security-update.htmlRelease Notes, Third Party Advisory

Timeline

Published: Mar 10, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-24025?

How severe is CVE-2021-24025?

CVE-2021-24025 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.66% probability of exploitation in the next 30 days.

How do I fix CVE-2021-24025?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-24025?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST