PatchTheCVECVE-2025-53539: FastAPI Guard is a security library for FastAPI that provides middleware to control IPs, log requests, and det
CVE-2025-53539 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, and detect penetration attempts. fastapi-guard's penetration attempts detection uses regex to scan incoming requests. However, some of the regex patterns used in detection are extremely inefficient and can cause polynomial complexity backtracks when handling specially crafted inputs. This vulnerability is fixed in 3.0.1.
Why this priority
- High severity
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 7.5 (High) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 0.5% (top 59%) |
| CISA exploited list | No |
| Weakness | CWE-1333 |
| Published | 2025-07-07 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
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-2025-53539?
fastapi guard: upgrade to 3.0.1. Exact commands for each OS are on this page.
Is CVE-2025-53539 being exploited?
CVE-2025-53539 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-2025-53539 affect?
CVE-2025-53539 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, and detect penetration attempts. fastapi-guard's penetration attempts detection uses regex to scan incoming requests. However, some of th
How urgent is CVE-2025-53539?
Priority 47/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action
Software pages
Related CVEs
- CVE-2025-54365 HIGH 7.5 DOWNGRADE fastapi-guard is a security library for FastAPI that provides middleware to control IPs, log requests, detect
- 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