CVE-2021-32723Network attack vector

Service hang via exponential regex backtracking

Published Jun 28, 2021 · Updated Aug 3, 2024

Regular expression denial of service in Prism before 1.24.0 allows remote attackers to hang syntax highlighting with crafted text. Regex patterns in the ASCIIDoc and ERB language grammars perform exponential backtracking while matching adversarial input. The consuming application must highlight untrusted text with either affected grammar; other Prism language grammars are not affected.

CVSS severity7.4
High
EPSS probability1.43%
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 Prism before 1.24.0 allows remote attackers to hang syntax highlighting with crafted text. Regex patterns in the ASCIIDoc and ERB language grammars perform exponential backtracking while matching adversarial input. The consuming application must highlight untrusted text with either affected grammar; other Prism language grammars are not affected.

The record

CVE
CVE-2021-32723
Published
Jun 28, 2021
Updated
Aug 3, 2024
Vendor
PrismJS
Product
Prism
Classifications
CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 28, 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=< 1.24

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PrismJS · Prismversion=< 1.24

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
7.4GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:N/A:H
4.3NIST NVDAV:N/AC:M/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.

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 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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