CVE-2021-29060Public exploitNetwork attack vector

Service interruption via HWB regex backtracking

Published Jun 21, 2021 · Updated Aug 3, 2024

Regular expression denial of service in color-string before 1.5.5 allows remote attackers to interrupt service via crafted invalid HWB strings. The cs.get.hwb parser applies an ambiguous hue-number regular expression whose adjacent unbounded quantifiers trigger excessive backtracking on long invalid values. An application must pass attacker-controlled CSS color text to the library; processing time rises sharply, while confidentiality and integrity remain unaffected.

CVSS severity5.3
Medium
EPSS probability3.13%
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 color-string before 1.5.5 allows remote attackers to interrupt service via crafted invalid HWB strings. The cs.get.hwb parser applies an ambiguous hue-number regular expression whose adjacent unbounded quantifiers trigger excessive backtracking on long invalid values. An application must pass attacker-controlled CSS color text to the library; processing time rises sharply, while confidentiality and integrity remain unaffected.

The record

CVE
CVE-2021-29060
Published
Jun 21, 2021
Updated
Aug 3, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-770, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 21, 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?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P
5.3NIST NVDCVSS: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.

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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 exploitPublished

Weakness, pattern, technique

CWE-770Allocation of Resources Without Limits or Throttling
T1499.004Endpoint Denial of Service: Application 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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