What’s Vulnerable › Vulnerabilities

CVE-2026-55520: Protego: Exponential backtracking ReDoS in robots.txt URL wildcard matching

• Severity: high (CVSS 7.1 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-28 · updated 2026-09-09
• Weakness: CWE-400

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.

Affected products

• scrapy protego: before 0.6.2

References

• 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

Get alerted when CVE-2026-55520 or the next vulnerability affects your stack