CVE-2021-45115Network attack vector

Service interruption via oversized password comparison

Published Jan 4, 2022 · Updated Aug 4, 2024

Denial of service in Django 2.2 through 2.2.25, 3.2 through 3.2.10, and 4.0 allows remote attackers to interrupt service. UserAttributeSimilarityValidator passes an oversized submitted password and short user attributes to difflib.SequenceMatcher.quick_ratio() without first eliminating length ratios that cannot meet the similarity threshold. Reachability requires unrestricted registration with this validator enabled, and repeated expensive comparisons can exhaust application workers.

CVSS severity8.7
High
EPSS probability2.42%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Django 2.2 through 2.2.25, 3.2 through 3.2.10, and 4.0 allows remote attackers to interrupt service. UserAttributeSimilarityValidator passes an oversized submitted password and short user attributes to difflib.SequenceMatcher.quick_ratio() without first eliminating length ratios that cannot meet the similarity threshold. Reachability requires unrestricted registration with this validator enabled, and repeated expensive comparisons can exhaust application workers.

The record

CVE
CVE-2021-45115
Published
Jan 4, 2022
Updated
Aug 4, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-400, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 4, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record 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:N/SI:N/SA:N
7.5GitHub Advisory DatabaseCVSS:3.1/AV:N/AC:L/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-400Uncontrolled Resource Consumption
T1499.003Application Exhaustion Flood

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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