Protego: Exponential backtracking ReDoS in robots.txt URL wildcard matching (CVE-2026-55520) | HOL Guard CVE

High severityCVE-2026-55520GHSA-WJMF-P669-5M5P

Protego: Exponential backtracking ReDoS in robots.txt URL wildcard matching

Answer in brief

CVE-2026-55520 records a High severity vulnerability in Protego: Exponential backtracking ReDoS in robots.txt URL wildcard matching. The current sources do not mark it as known exploited. The current feed maps scrapy/protego (generic), Protego (pip). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 28, 2026Updated Aug 28, 2026Source checked Aug 28, 2026First seen by HOL Aug 28, 2026Material review Aug 28, 2026

Upstream Advisory

Key facts

Risk: High
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps scrapy/protego (generic), Protego (pip). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
scrapy/protegogeneric	< 0.6.2	Not reported
Protegopip	<=0.6.1	0.6.2

Recommended response

Check inventory. Check lockfiles and deployed manifests for scrapy/protego, Protego.
Review the reported fix. Update Protego to 0.6.2 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Aug 28, 2026
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
Aug 28, 2026

Sources and claim methodology

Upstream source description

Protego is a pure-Python robots.txt parser with support for modern conventions. Prior to 0.6.2, protego._urlpattern._URLPattern._prepare_pattern_for_regex translates every asterisk in an Allow or Disallow directive into a lazy regular-expression wildcard, so a directive containing many asterisks creates exponential backtracking. After protego.Protego.parse processes a crafted robots.txt file, protego.Protego.can_fetch can spend an attacker-controlled period matching a near-miss URL and deny service to the crawler. The vulnerable path is src/protego/_urlpattern.py in the _URLPattern match logic. This issue is fixed in version 0.6.2.

Quoted source text, attributed separately from HOL analysis.