{"id":"UBUNTU-CVE-2026-55520","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.","modified":"2026-09-02T19:41:06.541440867Z","published":"2026-08-28T20:18:00Z","upstream":["CVE-2026-55520"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-55520"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-55520"},{"type":"REPORT","url":"https://github.com/scrapy/protego/security/advisories/GHSA-wjmf-p669-5m5p"}],"affected":[{"package":{"name":"python-protego","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/python-protego?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.1.16+dfsg-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-protego","binary_version":"0.1.16+dfsg-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55520.json"}},{"package":{"name":"python-protego","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/python-protego?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.1.16+dfsg-2","0.1.16+dfsg-3","0.2.1+dfsg-1"],"ecosystem_specific":{"binaries":[{"binary_version":"0.2.1+dfsg-1","binary_name":"python3-protego"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55520.json"}},{"package":{"name":"python-protego","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/python-protego?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.2.1+dfsg-1","0.3.0+dfsg-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-protego","binary_version":"0.3.0+dfsg-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55520.json"}},{"package":{"name":"python-protego","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/python-protego?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.4.0+dfsg-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-protego","binary_version":"0.4.0+dfsg-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-55520.json"}},{"package":{"name":"python-protego","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/python-protego?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.4.0+dfsg-1","0.5.0+dfsg-1","0.6.0+dfsg-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-protego","binary_version":"0.6.0+dfsg-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-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"},{"type":"Ubuntu","score":"medium"}]}