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TI-2020-05527 Aliases CVE-2020-6817GHSA-vqhp-cxgc-6wmm

Regular expression denial of service in Mozilla Bleach

Priority HIGH 72CWE-1333Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Fixed

Attack profile from CVSS 3.1 · CISA ADP. Fix status from CNA and GitHub. Impact type from CWE-1333.

Summary

bleach.clean behavior parsing style attributes could result in a regular expression denial of service (ReDoS). Calls to bleach.clean with an allowed tag with an allowed style attribute are vulnerable to ReDoS. For example, bleach.clean(..., attributes={'a': ['style']}).

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00718 54th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed Mozilla Bleach (Mozilla): 3.1.4bleach (PyPI): 3.1.4

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
MozillaMozilla Bleachbefore 3.1.43.1.4Patch availableCNA
—bleach (PyPI)before 3.1.43.1.4Patch availableGHSA-vqhp-cxgc-6wmm
  • Mozilla Bleach VendorMozilla Affected before 3.1.4 Fixed in 3.1.4 Patch available CNA
  • bleach (PyPI) Vendor— Affected before 3.1.4 Fixed in 3.1.4 Patch available GHSA-vqhp-cxgc-6wmm

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:mozilla:bleach:*:*:*:*:*:*:*:*before 3.1.4VulnerableMozilla
  • cpe:2.3:a:mozilla:bleach:*:*:*:*:*:*:*:* Versions before 3.1.4 Vulnerable ·Mozilla

Remediation

  • Fix · CNA Mozilla Bleach (Mozilla) Fixed in 3.1.4
  • Fix · GHSA-vqhp-cxgc-6wmm bleach (PyPI) Fixed in 3.1.4 Advisory →

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2020-6817
  2. 2026-10-03 Alias added: GHSA-vqhp-cxgc-6wmm

References

Exploit 1

Advisory 2

Other 3

  • TI-2021-06301 Cross-site scripting in Mozilla Bleach CVSS 3.1MEDIUM 6.1
  • TI-2018-05596 An issue was discovered in Bleach 2.1.x before 2.1.3. CVSS 3.0CRITICAL 9.8
  • TI-2020-05512 Cross-site scripting in Mozilla Bleach CVSS 3.1MEDIUM 6.1
  • TI-2020-05526 Cross-site scripting in Mozilla Bleach CVSS 3.1MEDIUM 6.1

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences