CVE-2026-23996— FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection
Quick assessment
Affected
Athroniaeth fastapi-api-key
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
FastAPI Api Key是Athroniaeth个人开发者的一个安全密钥库。 FastAPI Api Key 1.1.0版本存在安全漏洞，该漏洞源于verify_key方法存在时序侧信道，可能导致攻击者通过测量响应延迟来推断API密钥的有效性。
Possible ATT&CK Techniques 1 AI
T1115 · Clipboard Data
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I. Basic Information for CVE-2026-23996
Vulnerability Information
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Vulnerability Title
FastAPI Api Key has a timing side-channel in verify_key that allows statistical key validity detection
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
通过时间差异性导致的信息暴露
Source: CVE Program / CVE List V5
Vulnerability Title
FastAPI Api Key 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
FastAPI Api Key是Athroniaeth个人开发者的一个安全密钥库。 FastAPI Api Key 1.1.0版本存在安全漏洞，该漏洞源于verify_key方法存在时序侧信道，可能导致攻击者通过测量响应延迟来推断API密钥的有效性。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| Athroniaeth | fastapi-api-key | < 1.1.0 | - |
|
II. Public POCs for CVE-2026-23996
| # | POC Description | Source Link | Shenlong Link |
|---|
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IV. Related Vulnerabilities
Same weakness: CWE-208
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V. Comments for CVE-2026-23996
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