{"id":"CVE-2026-55520","summary":"Protego: Exponential backtracking ReDoS in robots.txt URL wildcard matching","details":"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.","aliases":["GHSA-wjmf-p669-5m5p","PYSEC-2026-3906"],"modified":"2026-09-11T03:30:15.626087069Z","published":"2026-08-28T18:42:38.334Z","related":["openSUSE-SU-2026:11202-1"],"database_specific":{"cwe_ids":["CWE-1333","CWE-400"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55520.json","cna_assigner":"GitHub_M"},"references":[{"type":"WEB","url":"https://github.com/scrapy/protego/releases/tag/0.6.2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55520.json"},{"type":"ADVISORY","url":"https://github.com/scrapy/protego/security/advisories/GHSA-wjmf-p669-5m5p"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55520"},{"type":"FIX","url":"https://github.com/scrapy/protego/commit/785940181659bf440ba82f1da148fade5087e858"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/scrapy/protego","events":[{"introduced":"0"},{"fixed":"785940181659bf440ba82f1da148fade5087e858"},{"fixed":"efe5039d39ee51f117acd0b01ffd8109ae265c22"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"fixed":"0.6.2"}],"source":["AFFECTED_FIELD","REFERENCES"]}}],"versions":["0.6.1","0.6.0","0.5.0","0.4.0","0.3.1","0.3.0","0.2.1","0.2.0","0.1.16","0.1.15","0.1.14","0.1.13","0.1.12","0.1.11","0.1.10","0.1.9","0.1.8","0.1.7","0.1.6","v0.1.2","0.1.5","0.1.4","0.1.3","v0.1.1","v0.1"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55520.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}