Vulnerability · Published Aug 28, 2026 · Assigned by GitHub_M

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

High 7.1

In plain English

A high-severity uncontrolled resource consumption in protego from scrapy. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 4.0)7.1High

Exploit odds (30 days)0.5%top 56.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	python-protego	no fix listed	DEBIAN-CVE-2026-55520
Debian:13	python-protego	no fix listed	DEBIAN-CVE-2026-55520
Debian:14	python-protego	0.6.2+dfsg-1	DEBIAN-CVE-2026-55520
PyPI	protego	0.6.2	GHSA-wjmf-p669-5m5p
PyPI	protego	0.6.2	PYSEC-2026-3906
Ubuntu:22.04:LTS	python-protego	no fix listed	UBUNTU-CVE-2026-55520
Ubuntu:24.04:LTS	python-protego	no fix listed	UBUNTU-CVE-2026-55520
Ubuntu:25.10	python-protego	no fix listed	UBUNTU-CVE-2026-55520
Ubuntu:26.04:LTS	python-protego	no fix listed	UBUNTU-CVE-2026-55520
Ubuntu:26.10	python-protego	no fix listed	UBUNTU-CVE-2026-55520

Affected products (as reported)

Vendor	Product	Versions
scrapy	protego	< 0.6.2

Weakness: CWE-400, CWE-1333 · Vector: 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

References

https://github.com/scrapy/protego/security/advisories/GHSA-wjmf-p669-5m5p x_refsource_CONFIRM
https://github.com/scrapy/protego/commit/785940181659bf440ba82f1da148fade5087e858 x_refsource_MISC
https://github.com/scrapy/protego/releases/tag/0.6.2 x_refsource_MISC