CVE-2021-36716Network attack vector

Service interruption via backtracking email validation

Published Jul 14, 2021 · Updated Aug 4, 2024

Regular expression denial of service in Segment is-email before 1.0.1 allows attackers to cause excessive CPU use via crafted email input. The isEmail(input) function applies a backtracking-prone email-validation expression to an attacker-controlled string, making matching computationally expensive. Applications are exposed only when untrusted values reach this function, and sustained matching can interrupt service by consuming application CPU time.

CVSS severity7.5
High
EPSS probability0.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Segment is-email before 1.0.1 allows attackers to cause excessive CPU use via crafted email input. The isEmail(input) function applies a backtracking-prone email-validation expression to an attacker-controlled string, making matching computationally expensive. Applications are exposed only when untrusted values reach this function, and sustained matching can interrupt service by consuming application CPU time.

The record

CVE
CVE-2021-36716
Published
Jul 14, 2021
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 14, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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