CVE-2021-23341Network attack vector

Unauthenticated service interruption via vulnerable regexes

Published Feb 18, 2021 · Updated Sep 16, 2024

Regular Expression Denial of Service in PrismJS Prism before 1.23.0 allows remote attackers to interrupt service via crafted text. The prism-asciidoc, prism-rest, prism-tap and prism-eiffel grammars use regex patterns that can undergo excessive backtracking on attacker-controlled input. Exploitation requires an application to pass untrusted text to an affected grammar and can consume CPU until the processing service hangs or becomes unavailable.

CVSS severity7.5
High
EPSS probability3.17%
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 PrismJS Prism before 1.23.0 allows remote attackers to interrupt service via crafted text. The prism-asciidoc, prism-rest, prism-tap and prism-eiffel grammars use regex patterns that can undergo excessive backtracking on attacker-controlled input. Exploitation requires an application to pass untrusted text to an affected grammar and can consume CPU until the processing service hangs or becomes unavailable.

The record

CVE
CVE-2021-23341
Published
Feb 18, 2021
Updated
Sep 16, 2024
Vendor
PrismJS
Product
Prism
Classifications
CWE-400, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Feb 18, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 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=unspecified <1.23.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PrismJS · Prismversion=unspecified <1.23.0

Published CVSS scores

7.5NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NVDAV: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 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-400Uncontrolled Resource Consumption
T1499.002Service Exhaustion

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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