CVE-2025-54365: fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect

This week

HIGH 7.5REMOTEDOWNGRADE

CVE-2025-54365 is a high-severity flaw (CVSS 7.5) affecting fastapi guard. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect penetration attempts and more. In version 3.0.1, the regular expression patched to mitigate the ReDoS vulnerability by limiting the length of string fails to catch inputs that exceed this limit. This type of patch fails to detect cases in which the string representing the attributes of a <script> tag exceeds 100 characters. As a result, m

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 41%)
CISA exploited list	No
Weakness	CWE-20, CWE-185, CWE-1333
Published	2025-07-23
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: fastapi-guard

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2025-07-23 23:15 UTCPublished CVE record published
2026-06-17 09:39 UTCUpdated Record last modified

fastapi-guard fastapi guard DOWNGRADE

Affected: 3.0.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.0.1

1. Check installed version

apt-cache policy fastapi-guard || rpm -q fastapi-guard || fastapi-guard --version

2. No fixed release: DOWNGRADE to a release before 3.0.1 (Debian / Ubuntu)

apt-cache madison fastapi-guard sudo apt install fastapi-guard=<VERSION_BEFORE_3.0.1> sudo apt-mark hold fastapi-guard

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list fastapi-guard sudo dnf downgrade fastapi-guard-<VERSION_BEFORE_3.0.1> sudo dnf versionlock add fastapi-guard

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2025-54365?

fastapi guard: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2025-54365 being exploited?

CVE-2025-54365 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2025-54365 affect?

CVE-2025-54365 affects fastapi guard. Severity is high (CVSS 7.5). fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect penetration attempts and more. In version 3.0.1, the regular expression patched to mitigate the ReDoS vulnerability by limiting th

How urgent is CVE-2025-54365?

Priority 51/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

FastAPI vulnerabilities

Related CVEs

CVE-2025-53539 HIGH 7.5 UPGRADE FastAPI Guard is a security library for FastAPI that provides middleware to control IPs, log requests, and det
CVE-2025-46814 LOW 3.4 UPGRADE FastAPI Guard is a security library for FastAPI that provides middleware to control IPs, log requests, and det

References

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