CVE-2023-23556Network attack vector

Code execution via noncanonical BigInt conversion

Published May 18, 2023 · Updated Jan 31, 2025

Out-of-bounds write in Meta Hermes before commit a6dcafe6ded8e61658b40f5699878cd19a481f80 allows attackers to execute arbitrary code. BigIntSupport::toDouble passed a noncanonical NaN from APInt::roundToDouble when converting BigInts longer than two digits, allowing the invalid result to reach memory-writing logic. Exploitation requires a deployment that executes untrusted JavaScript; most React Native applications do not expose that condition.

CVSS severity9.8
Critical
EPSS probability0.89%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds write in Meta Hermes before commit a6dcafe6ded8e61658b40f5699878cd19a481f80 allows attackers to execute arbitrary code. BigIntSupport::toDouble passed a noncanonical NaN from APInt::roundToDouble when converting BigInts longer than two digits, allowing the invalid result to reach memory-writing logic. Exploitation requires a deployment that executes untrusted JavaScript; most React Native applications do not expose that condition.

The record

CVE
CVE-2023-23556
Published
May 18, 2023
Updated
Jan 31, 2025
Vendor
Meta Platforms, Inc.
Product
Hermes
Classifications
CWE-787, T1203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 18, 2023CVE publishedPublication date reported by the CVE source.
  2. Jan 31, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <a6dcafe6ded8e61658b40f5699878cd19a481f80

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Meta Platforms, Inc. · Hermesversion=0 <a6dcafe6ded8e61658b40f5699878cd19a481f80

Published CVSS scores

9.8NISTCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1203Exploitation for Client Execution

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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