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.
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Affected Vendors & Products
References
History
Fri, 28 Aug 2026 19:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| 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. | |
| Title | Protego: Exponential backtracking ReDoS in robots.txt URL wildcard matching | |
| Weaknesses | CWE-1333 CWE-400 |
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cvssV4_0
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Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-08-28T18:42:38.334Z
Reserved: 2026-06-16T22:44:22.284Z
Link: CVE-2026-55520
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Status : Received
Published: 2026-08-28T20:18:28.100
Modified: 2026-08-28T20:18:28.100
Link: CVE-2026-55520
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OpenCVE Enrichment
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