CVE-2025-54363Public exploit

Local CPU exhaustion via docstring regex backtracking

Published Aug 20, 2025 · Updated Aug 21, 2025

Regular expression denial of service in Microsoft Knack 0.12.0 allows local users to exhaust CPU through crafted docstrings. The extract_full_summary_from_signature function applies overlapping whitespace quantifiers to docstrings lacking a terminating colon, causing catastrophic backtracking. Reachability requires control of source-code docstrings; the maintainer states that the parser does not process user input and exposes no attack surface.

CVSS severity6.9
Medium
EPSS probability0.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Regular expression denial of service in Microsoft Knack 0.12.0 allows local users to exhaust CPU through crafted docstrings. The extract_full_summary_from_signature function applies overlapping whitespace quantifiers to docstrings lacking a terminating colon, causing catastrophic backtracking. Reachability requires control of source-code docstrings; the maintainer states that the parser does not process user input and exposes no attack surface.

The record

CVE
CVE-2025-54363
Published
Aug 20, 2025
Updated
Aug 21, 2025
Vendor
Microsoft
Product
Knack
Classifications
CWE-1333, T1499.004
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 20, 2025CVE publishedPublication date reported by the CVE source.
  2. Aug 21, 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?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.12.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

Microsoft · Knackversion=0.12.0

Published CVSS scores

1.2GitHubCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U
6.9MITRECVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1333Inefficient Regular Expression Complexity
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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