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Vulnerability record · CVE-2026-55520 · published 28 August 2026

CVE-2026-55520: Uncontrolled resource consumption vulnerability

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.

7.1 CVSS 4.0 High EPSS 0.51% · top 58.8% CWE-400 · Uncontrolled resource consumptionCWE-1333 · Inefficient regular expression (ReDoS) Deferred
7.1CVSS 4.0 base score
0.51%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
9 Sep 2026Last modified by NVD

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/scrapy/protego/commit/785940181659bf440ba82f1da148fade5087e858
https://github.com/scrapy/protego/releases/tag/0.6.2
https://github.com/scrapy/protego/security/advisories/GHSA-wjmf-p669-5m5p

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Source: NIST National Vulnerability Database (record CVE-2026-55520), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.