CVE-2023-4316Public exploitNetwork attack vector

Server crash via exponential email-regex backtracking

Published Sep 28, 2023 · Updated Dec 3, 2025

Inefficient regular expression complexity in Zod 3.21.0 through 3.22.3 allows remote attackers to crash servers via email validation. The emailRegex used by z.string().email() applies a quantified group containing an optional dot to attacker-controlled strings, causing exponential backtracking on crafted invalid addresses. Exposure requires an application to pass remotely supplied email values into this validator; CPU exhaustion can leave the hosting server unresponsive.

CVSS severity7.5
High
EPSS probability0.76%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Inefficient regular expression complexity in Zod 3.21.0 through 3.22.3 allows remote attackers to crash servers via email validation. The emailRegex used by z.string().email() applies a quantified group containing an optional dot to attacker-controlled strings, causing exponential backtracking on crafted invalid addresses. Exposure requires an application to pass remotely supplied email values into this validator; CPU exhaustion can leave the hosting server unresponsive.

The record

CVE
CVE-2023-4316
Published
Sep 28, 2023
Updated
Dec 3, 2025
Vendor
colinhacks
Product
Zod
Classifications
CWE-1333, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 28, 2023CVE publishedPublication date reported by the CVE source.
  2. Dec 3, 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=3.21.0 <=3.22.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

colinhacks · Zodversion=3.21.0 <=3.22.3

Published CVSS scores

7.5Fluid AttacksCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.3GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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.

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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 exploitPublished

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499.004Application or System Exploitation Flood

Public exploit references

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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