CVE-2021-23382Public exploitNetwork attack vector

Processing hang via backtracking source-map regexes

Published Apr 26, 2021 · Updated Sep 16, 2024

Regular expression denial of service in PostCSS before 8.2.13 allows remote attackers to interrupt CSS processing via crafted input. The getAnnotationURL() and loadAnnotation() methods in lib/previous-map.js apply backtracking regular expressions to attacker-controlled sourceMappingURL comments. Reachability requires a consuming application to pass untrusted CSS to PostCSS; exploitation consumes CPU and can hang that processing path.

CVSS severity5.3
Medium
EPSS probability2.51%
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 PostCSS before 8.2.13 allows remote attackers to interrupt CSS processing via crafted input. The getAnnotationURL() and loadAnnotation() methods in lib/previous-map.js apply backtracking regular expressions to attacker-controlled sourceMappingURL comments. Reachability requires a consuming application to pass untrusted CSS to PostCSS; exploitation consumes CPU and can hang that processing path.

The record

CVE
CVE-2021-23382
Published
Apr 26, 2021
Updated
Sep 16, 2024
Vendor
PostCSS
Product
PostCSS
Classifications
CWE-400, CAPEC-492, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 26, 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 <8.2.13

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

PostCSS · PostCSSversion=unspecified <8.2.13

Published CVSS scores

5.3GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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-400Uncontrolled Resource Consumption
CAPEC-492Regular Expression Exponential Blowup
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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