CVE-2022-40897Network attack vector

Package-index processing hang via unbounded regex backtracking

Published Dec 22, 2022 · Updated Nov 4, 2025

ReDoS in PyPA setuptools 65.5.0 and earlier allows remote attackers to hang package-index processing through crafted HTML. The package_index.py REL expression accepts unbounded whitespace around the rel attribute's equals sign, forcing excessive backtracking on hostile input. The target process must fetch an attacker-controlled package page or custom PackageIndex page; CPU exhaustion then hangs index parsing.

CVSS severity8.7
High
EPSS probability2.62%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

ReDoS in PyPA setuptools 65.5.0 and earlier allows remote attackers to hang package-index processing through crafted HTML. The package_index.py REL expression accepts unbounded whitespace around the rel attribute's equals sign, forcing excessive backtracking on hostile input. The target process must fetch an attacker-controlled package page or custom PackageIndex page; CPU exhaustion then hangs index parsing.

The record

CVE
CVE-2022-40897
Published
Dec 22, 2022
Updated
Nov 4, 2025
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-1333, CAPEC-492, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 22, 2022CVE publishedPublication date reported by the CVE source.
  2. Nov 4, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

8.7GitHub Advisory DatabaseCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:L/SI:L/SA:N
5.9GitLab Advisory DatabaseCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
CAPEC-492Regular Expression Exponential Blowup
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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