CVE-2020-26310Public exploitNetwork attack vector

Service interruption via exponential regex backtracking

Published Oct 26, 2024 · Updated Oct 28, 2024

ReDoS in blowsie Pure JavaScript HTML5 Parser version 0 allows remote attackers to interrupt service via crafted HTML input. The parser applies ambiguous startTag and attr regular expressions to attacker-controlled HTML, causing exponential backtracking and sustained CPU use. Exposure requires a consuming application to pass untrusted HTML into the library; the bounded consequence is CPU exhaustion and service interruption.

CVSS severity8.7
High
EPSS probability0.41%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

ReDoS in blowsie Pure JavaScript HTML5 Parser version 0 allows remote attackers to interrupt service via crafted HTML input. The parser applies ambiguous startTag and attr regular expressions to attacker-controlled HTML, causing exponential backtracking and sustained CPU use. Exposure requires a consuming application to pass untrusted HTML into the library; the bounded consequence is CPU exhaustion and service interruption.

The record

CVE
CVE-2020-26310
Published
Oct 26, 2024
Updated
Oct 28, 2024
Vendor
blowsie
Product
Pure JavaScript HTML5 Parser
Classifications
CWE-1333, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 26, 2024CVE publishedPublication date reported by the CVE source.
  2. Oct 28, 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
  2. Affected versionversion=0 <*

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

blowsie · Pure JavaScript HTML5 Parserversion=0; version=0 <*

Published CVSS scores

8.7GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/U:Green

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 9, 2026Sep 15, 2026
Latest reporting daySep 15, 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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