Security readout for executives and security teams
Plain-English summary
CVE-2020-26303 affects the insane HTML sanitizer. A maliciously crafted input can make vulnerable regular expressions consume excessive CPU, causing denial of service. The cited description says versions 2.6.2 and prior are affected and that no known patches were available at publication.
Executive priority
Prioritize if customer-facing services process user-submitted HTML with insane. The main business risk is service degradation or outage, not data theft, based on the supplied CVSS and description.
Technical view
The issue is CWE-1333 ReDoS in one or more regular expressions used by insane, a whitelist-oriented HTML sanitizer. CVSS 4.0 rates it 8.7 with network attack vector, low complexity, no privileges, no user interaction, and high vulnerable-system availability impact.
Likely exposure
Exposure is likely in web applications, APIs, or background processors that use insane 2.6.2 or earlier to sanitize remotely supplied HTML or rich text. The source bundle does not provide CPEs or complete deployment indicators.
Exploitation context
The source bundle does not show known active exploitation, and KEV is false. Public advisory and GitHub issue information exists, so defenders should treat details as publicly known while avoiding assumptions about weaponized exploitation.
Researcher notes
Evidence supports ReDoS and high availability impact, but patch state is only described as unavailable at publication. The affected-version metadata is inconsistent, so rely on the advisory text and verify package usage directly.
Mitigation direction
- Inventory applications and lockfiles for insane usage and versions.
- Check the GitHub issue and vendor guidance for patch status.
- Reduce reliance on insane for untrusted HTML until a safe version is confirmed.
- Apply request, CPU, and queue limits around sanitizer execution paths.
- Consider alternative maintained sanitization controls after engineering review.
Validation and detection
- Confirm whether deployed versions are 2.6.2 or earlier.
- Map all paths passing user-controlled HTML into insane.
- Review monitoring for CPU saturation tied to HTML sanitization workloads.
- Check whether vulnerable code runs synchronously on public request paths.
- Document compensating controls and remaining availability risk.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CWE-1333: Exact CWE lookup
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Open ATT&CK lookupCVE-2020-26303 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 8.7 (4.0)
- Known Exploited
- No
- Published
Vector: 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
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
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——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
8.7HighVector: 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
Source materials
- CVE List V5 sourceCVE List V5
- https://securitylab.github.com/advisories/GHSL-2020-289-redos-insane/CVE reference
- https://github.com/bevacqua/insane/issues/19CVE reference
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Inefficient Regular Expression Complexity
Inefficient Regular Expression Complexity represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.