FastAPI Api Key provides a backend-agnostic library that provides an API key system. Version 1.1.0 has a timing side-channel vulnerability in verify_key(). The method applied a random delay only on verification failures, allowing an attacker to statistically distinguish valid from invalid API keys by measuring response latencies. With enough repeated requests, an adversary could infer whether a key_id corresponds to a valid key, potentially accelerating brute-force or enumeration attacks. All users relying on verify_key() for API key authentication prior to the fix are affected. Users should upgrade to version 1.1.0 to receive a patch. The patch applies a uniform random delay (min_delay to max_delay) to all responses regardless of outcome, eliminating the timing correlation. Some workarounds are available. Add an application-level fixed delay or random jitter to all authentication responses (success and failure) before the fix is applied and/or use rate limiting to reduce the feasibility of statistical timing attacks.
Metrics
Affected Vendors & Products
No data.
No data.
No data.
No data.
Advisories
| Source | ID | Title |
|---|---|---|
 Github GHSA |
GHSA-95c6-p277-p87g | FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection |
Fixes
Solution
No solution given by the vendor.
Workaround
No workaround given by the vendor.
References
History
Wed, 21 Jan 2026 22:45:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | FastAPI Api Key provides a backend-agnostic library that provides an API key system. Version 1.1.0 has a timing side-channel vulnerability in verify_key(). The method applied a random delay only on verification failures, allowing an attacker to statistically distinguish valid from invalid API keys by measuring response latencies. With enough repeated requests, an adversary could infer whether a key_id corresponds to a valid key, potentially accelerating brute-force or enumeration attacks. All users relying on verify_key() for API key authentication prior to the fix are affected. Users should upgrade to version 1.1.0 to receive a patch. The patch applies a uniform random delay (min_delay to max_delay) to all responses regardless of outcome, eliminating the timing correlation. Some workarounds are available. Add an application-level fixed delay or random jitter to all authentication responses (success and failure) before the fix is applied and/or use rate limiting to reduce the feasibility of statistical timing attacks. | |
| Title | FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection | |
| Weaknesses | CWE-208 | |
| References |
| |
| Metrics |
cvssV3_1
|
Projects
Sign in to view the affected projects.
MITRE
Status: PUBLISHED
Assigner: GitHub_M
Published:
Updated: 2026-01-21T22:29:24.107Z
Reserved: 2026-01-19T18:49:20.658Z
Link: CVE-2026-23996
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-01-21T23:15:53.090
Modified: 2026-01-21T23:15:53.090
Link: CVE-2026-23996
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses