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

Quick assessment

Affected
scrapy protego
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Protego 是一个纯 Python 编写的 robots.txt 解析器，支持现代约定。在 0.6.2 版本之前， 方法会将 Allow 或 Disallow 指令中的每个星号（ ）转换为懒惰正则表达式通配符，因此，包含大量星号的指令会引发指数级回溯（exponential backtracking）。在 处理了经过精心构造的 robots.txt 文件后， 在匹配一个几乎不匹配的 URL 时可能花费攻击者可控的时间，从而对爬虫造成拒绝服务（DoS）影响。存在漏洞的代码路径位于 中的 匹配逻辑。该问题已在 0.

CVSS 7.1 · High

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
scrapy protego < 0.6.2 affected
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I. Basic Information for CVE-2026-55520

Vulnerability Information
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Vulnerability Title
Protego: Exponential backtracking ReDoS in robots.txt URL wildcard matching
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
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
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
scrapy protego < 0.6.2 -

II. Public POCs for CVE-2026-55520

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III. Intelligence Information for CVE-2026-55520

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Patches & Fixes for CVE-2026-55520 (1)

Vendor Advisories for CVE-2026-55520 (1)

Vendor Pages for CVE-2026-55520 (1)

IV. Related Vulnerabilities

Same vendor: scrapy
Same weakness: CWE-400

V. Comments for CVE-2026-55520

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