CVE-2021-43309Public exploitNetwork attack vector

Service interruption via exponential URI template backtracking

Published Aug 24, 2022 · Updated Aug 4, 2024

Regular expression denial of service in LiteJS URI Template Lite before 22.9.0 allows remote attackers to interrupt service via URI.expand input. The expandRe expression in index.js applies nested repetition while scanning an unterminated URI template, causing exponential backtracking on repeated variable-name characters. The calling application must pass attacker-controlled template text to URI.expand; crafted input can monopolize CPU and stall the hosting process.

CVSS severity5.9
Medium
EPSS probability0.97%
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 LiteJS URI Template Lite before 22.9.0 allows remote attackers to interrupt service via URI.expand input. The expandRe expression in index.js applies nested repetition while scanning an unterminated URI template, causing exponential backtracking on repeated variable-name characters. The calling application must pass attacker-controlled template text to URI.expand; crafted input can monopolize CPU and stall the hosting process.

The record

CVE
CVE-2021-43309
Published
Aug 24, 2022
Updated
Aug 4, 2024
Vendor
LiteJS
Product
URI Template Lite
Classifications
CWE-1333, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 24, 2022CVE 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?

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

  1. Affected versionversion=0 <22.9.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

LiteJS · URI Template Liteversion=0 <22.9.0

Published CVSS scores

5.9JFrogCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
7.5NIST NVDCVSS: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 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

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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