CVE-2021-32740Network attack vector

Application hang via catastrophic template-regex backtracking

Published Jul 6, 2021 · Updated Aug 3, 2024

Regular expression denial of service in Addressable 2.3.0 through 2.7.0 allows attackers to hang applications via crafted template matches. Addressable::Template#match uses a non-atomic variable-character group that lets a crafted nonmatch force catastrophic regex backtracking. Only applications that construct templates from untrusted input and perform URI-template matching expose the resource-exhaustion path; URI parsing alone is unaffected.

CVSS severity7.5
High
EPSS probability2.20%
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 Addressable 2.3.0 through 2.7.0 allows attackers to hang applications via crafted template matches. Addressable::Template#match uses a non-atomic variable-character group that lets a crafted nonmatch force catastrophic regex backtracking. Only applications that construct templates from untrusted input and perform URI-template matching expose the resource-exhaustion path; URI parsing alone is unaffected.

The record

CVE
CVE-2021-32740
Published
Jul 6, 2021
Updated
Aug 3, 2024
Vendor
Sporkmonger
Product
Addressable
Classifications
CWE-400, CWE-1333, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 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?

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

  1. Affected versionversion=> 2.3.0, <= 2.7.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Sporkmonger · Addressableversion=> 2.3.0, <= 2.7.0

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5GitHubCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 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
CWE-1333Inefficient Regular Expression Complexity
T1499.003Endpoint Denial of Service: Application Exhaustion Flood

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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