CVE-2023-23556

Name: CVE-2023-23556
Creator: NVD / NIST
Published: 2023-05-18T22:15:09.487+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 0.89%

Last modified Jun 17, 2026

CVE-2023-23556 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. An error in BigInt conversion to Number in Hermes prior to commit a6dcafe6ded8e61658b40f5699878cd19a481f80 could have been used by a malicious attacker to execute arbitrary code due to an out-of-bound write. Note that this bug is only exploitable in cases where Hermes is used to execute untrusted JavaScript. EPSS estimates a 0.89% chance of exploitation in the next 30 days.

Description

An error in BigInt conversion to Number in Hermes prior to commit a6dcafe6ded8e61658b40f5699878cd19a481f80 could have been used by a malicious attacker to execute arbitrary code due to an out-of-bound write. Note that this bug is only exploitable in cases where Hermes is used to execute untrusted JavaScript. Hence, most React Native applications are not affected.

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

0.89%

54.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-787

Affected Software

Vendor	Product	Versions
Facebook	Hermes	< 2023-02-02

References

https://github.com/facebook/hermes/commit/a6dcafe6ded8e61658b40f5699878cd19a481f80Patch
https://www.facebook.com/security/advisories/cve-2023-23556Patch, Vendor Advisory
https://github.com/facebook/hermes/commit/a6dcafe6ded8e61658b40f5699878cd19a481f80Patch
https://www.facebook.com/security/advisories/cve-2023-23556Patch, Vendor Advisory

Timeline

Published: May 18, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-23556?

How severe is CVE-2023-23556?

CVE-2023-23556 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 0.89% probability of exploitation in the next 30 days.

How do I fix CVE-2023-23556?

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-2023-23556?

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

Scan your code now

Source: NVD / NIST