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.
CVE-2026-55520
HIGHPre-NVD 7.17.1—Trending — 3 sources updated this week
EchelonGraph scoreMEDIUM confidence
This high-severity CVE scores 7.1 under a secondary CVSS source (NVD's own analysis pending). EPSS exploit probability: 0.4%, top 70% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
Triggered by: NVD CVSS baseline
Sources: epss, secondary
7.1EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
- High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 7.1Exploit: None knownExposed: 0
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 7.1
- EG Score
- 7.1(medium)
- EG Risk
- 37(Track)EG Risk 37/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity71% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 30%
- KEV
- Not listed
Published
August 28, 2026
Last Modified
August 28, 2026
Advisory Details (3)
Auto-updated Aug 28, 2026🔬 Proof of concept available. Patch available. Sources: github, github_commit, github_release.
github Patch Available🟡 PoC Available
Exponential backtracking ReDoS in robots.txt URL wildcard matching · Advisory · scrapy/protego · GitHub
https://github.com/scrapy/protego/security/advisories/GHSA-wjmf-p669-5m5pgithub_release Patch Available
Release 0.6.2 (scrapy/protego)
Patch available: scrapy/protego 0.6.2
https://github.com/scrapy/protego/releases/tag/0.6.2github_commit Patch Available
commit 785940181659 (scrapy/protego)
Patch available: scrapy/protego 0.6.2 (contains commit 785940181659)
https://github.com/scrapy/protego/commit/785940181659bf440ba82f1da148fade5087e858Vendor Advisories for CVE-2026-55520(1)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 5× in last 7d / 5× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-08-30 05:07 UTCEG score recompute
- 2026-08-30 01:22 UTCEPSS rescore
- 2026-08-28 20:24 UTCEG score recompute▲ 7.10
- 2026-08-28 20:24 UTCNVD updateCVSS v3 → 7.1 · CVSS v4 → 7.1
- 2026-08-28 19:10 UTCEG score recompute
Related CVEs(same CWE)
Same CWE
10 shownCWE-400
Frequently asked(5)
What is CVE-2026-55520?
CVE-2026-55520 is a high vulnerability published on August 28, 2026. Protego is a pure-Python robots.txt parser with support for modern conventions. Prior to 0.6.2, protego.urlpattern.URLPattern.preparepatternforregex translates every asterisk in an Allow or Disallow directive into a lazy regular-expression wildcard, so a directive containing many asterisks creates…
When was CVE-2026-55520 disclosed?
CVE-2026-55520 was first published in the National Vulnerability Database on August 28, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-55520 actively exploited?
CVE-2026-55520 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 70.3% of all scored CVEs.
What is the CVSS score of CVE-2026-55520?
CVE-2026-55520 has a CVSS v3 base score of 7.1 (NVD).
How do I remediate CVE-2026-55520?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-55520, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-55520
Is Your Infrastructure Affected by CVE-2026-55520?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.