---
id: CVE-2026-23996
aliases:
  - GHSA-95c6-p277-p87g
  - PYSEC-2026-1358
title: >-
  FastAPI Api Key has a timing side-channel in verify_key that allows
  statistical key validity detection
summary: >-
  FastAPI Api Key has a timing side-channel in verify_key that allows
  statistical key validity detection
severity: low
cvss: 3.7
cvssVector: 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N'
vendor: fastapi-api-key
product: fastapi-api-key
ecosystem: pip
affected:
  - fastapi-api-key < 1.1.0
patched:
  - fastapi-api-key 1.1.0
published: '2026-01-21'
updated: '2026-07-07'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-95c6-p277-p87g'
references:
  - url: >-
      https://github.com/Athroniaeth/fastapi-api-key/security/advisories/GHSA-95c6-p277-p87g
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-23996'
  - url: >-
      https://github.com/Athroniaeth/fastapi-api-key/commit/310b2c5c77305f38c63c0b917539a0344071dfd8
  - url: 'https://github.com/Athroniaeth/fastapi-api-key'
  - url: 'https://github.com/Athroniaeth/fastapi-api-key/releases/tag/1.1.0'
tags:
  - osv
  - pip
epss: 0.00298
epssPercentile: 0.20014
ingestedAt: '2026-07-08T18:25:47.753Z'
---

## Overview

### Impact
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.

Affected: all users relying on verify_key() for API key authentication prior to the fix.

### Patches
Yes. Users should upgrade to version 1.1.0 (or the version containing this fix). The patch applies a uniform random delay (min_delay to max_delay) to all responses regardless of outcome, eliminating the timing correlation.

### Workarounds
- Add an application-level fixed delay or random jitter to all authentication responses (success and failure) before the fix is applied.
- Use rate limiting to reduce the feasibility of statistical timing attacks.

### References
- CWE-208: Observable Timing Discrepancy
- Commit: 87b27640f77c5ef86c46311b6b5a7e2887e35b77
- OWASP: https://owasp.org/www-community/attacks/Timing_attack

## Affected packages

- `fastapi-api-key < 1.1.0`

## Remediation

Upgrade to a patched release:

- `fastapi-api-key 1.1.0`