5.3

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-44332

CVE-2026-44332: Fiber: Username Enumeration via Timing Oracle in BasicAuth Default Authorizer

Fiber is an Express inspired web framework written in Go. Prior to 3.3.0, the default Authorizer function in the BasicAuth middleware in middleware/basicauth/config.go uses short-circuit evaluation that skips password hash comparison for non-existent usernames, enabling reliable remote username enumeration through response timing differences. This issue is fixed in version 3.3.0.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-44332

CVE-2026-44332:

5.3

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

SSVC / BOD 26-04 ↗

Exploitation NoneAutomatable YesTech Impact Partial

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Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/gofiber/fiber/v3	go	<= 3.2.0	3.3.0

Technical Details

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Root Cause Analysis

The vulnerability is a timing oracle in the BasicAuth middleware's default Authorizer. The Authorizer function uses short-circuit evaluation, which causes a significant timing difference between requests with valid and invalid usernames. This allows an attacker to enumerate usernames by measuring response times. The patch mitigates this by ensuring that a password verification function is always called, even for non-existent users. This is achieved by introducing a dummyVerify function that performs a constant-time comparison against a pre-computed hash. The buildVerifiers function is modified to return this dummy verifier, and the Authorizer logic is updated to use it when a user is not found in the verifiers map. The fallbackDummyVerify function is the dummy verifier itself, and parseHashedPassword is also updated as part of the refactoring. These changes eliminate the timing discrepancy and prevent username enumeration.

Vulnerable functions

buildVerifiers

middleware/basicauth/config.go

This function was modified to introduce a dummy password verifier that is always executed for non-existent users, mitigating the timing oracle.

fallbackDummyVerify

middleware/basicauth/config.go

This function is the dummy verifier that is executed for non-existent users. The patch ensures that this function performs a constant-time comparison.

parseHashedPassword

middleware/basicauth/config.go

This function is responsible for parsing the hashed password and returning a verifier function. The change in the return type is part of the mitigation strategy.

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WAF Protection Rules

WAF Rule

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Reasoning

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