High
python-protego — security advisory
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.
- Products
- python-protego
- Affected versions
- 0.1.16+dfsg-1, 0.1.16+dfsg-2, 0.1.16+dfsg-3, 0.2.1+dfsg-1, 0.3.0+dfsg-1, 0.4.0+dfsg-1, 0.5.0+dfsg-1, 0.6.0+dfsg-1, 0.6.2+dfsg-1
- Fixed versions
- Not specified
- CVEs
- CVE-2026-55520
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 02:46 UTC · Revision 1
Source evidence
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.
osv:UBUNTU-CVE-2026-55520
python-protego
Fixed versions: Not specified
python-protego
Fixed versions: Not specified
python-protego
Fixed versions: Not specified
python-protego
Fixed versions: Not specified
python-protego
Fixed versions: Not specified
python-protego
Fixed versions: Not specified
Complete source record
{
"id": "e04c8934c03e7442bf1200a22f868346dbf4295fe32f9329fab90d927ea4aead",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2026-55520",
"method": "structured",
"payload": {
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"title": "UBUNTU-CVE-2026-55520",
"summary": "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.",
"evidence": "osv:UBUNTU-CVE-2026-55520",
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"severity": "high",
"structured": {
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"aliases": [
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"metrics": [
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{
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"modified": "2026-10-17T12:59:07.799702364Z",
"provider": "osv",
"upstream": [
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"references": [
"https://ubuntu.com/security/CVE-2026-55520",
"https://www.cve.org/CVERecord?id=CVE-2026-55520",
"https://github.com/scrapy/protego/security/advisories/GHSA-wjmf-p669-5m5p"
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"source_id": "core-osv",
"document_id": 359327,
"published_at": "2026-08-28T20:18:00+00:00"
}