# CVE-2025-54363: Denial of service in Knack

> An attacker can cause excessive CPU consumption and denial of service in applications using Microsoft Knack by injecting crafted docstrings.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 20 Aug 2025
- **Updated:** 21 Aug 2025
- **Also known as:** DEBIAN-CVE-2025-54363, UBUNTU-CVE-2025-54363

## What is CVE-2025-54363?

CVE-2025-54363 is a medium-severity denial of service vulnerability in Microsoft Knack, published on 20 Aug 2025. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Microsoft Knack 0.12.0 allows Regular expression Denial of Service (ReDoS) in the knack.introspection module. extract_full_summary_from_signature employs an inefficient regular expression pattern: "\s(:param)\s+(.+?)\s:(.*)" that is susceptible to catastrophic backtracking when processing crafted docstrings containing a large volume of whitespace without a terminating colon. An attacker who can control or inject docstring content into affected applications can trigger excessive CPU consumption. This software is used by Azure CLI.

Weakness: CWE-1333 (Inefficient Regular Expression Complexity)

## Which versions are affected by CVE-2025-54363?


## How do I fix CVE-2025-54363?

No fix has been published for CVE-2025-54363 yet. Limit exposure of the affected software until one is available.

## Is CVE-2025-54363 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-54363 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-54363 and fix it if it is affected.

What it is: CVE-2025-54363 is a medium-severity denial of service vulnerability in Microsoft Knack, published on 20 Aug 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-54363 exists.

Affected product: Microsoft Knack. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-54363/ (Markdown: https://insights.sbomify.com/CVE-2025-54363/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-54363
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-54363
- OSV: https://osv.dev/vulnerability/CVE-2025-54363

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From sbomify Insights: https://insights.sbomify.com/CVE-2025-54363/
Summaries are generated and may contain mistakes; the official description above is the record.