CVE-2026-44332

The default Authorizer function in GoFiber's BasicAuth middleware uses short-circuit evaluation that skips password hash comparison for non-existent usernames. With bcrypt-hashed passwords (the primary use case), the timing difference between a valid and invalid username is approximately 1,000,000:1 (~100ms vs ~100ns), enabling reliable remote username enumeration.

Vulnerable Code

File: middleware/basicauth/config.go, lines 126-138

if cfg.Authorizer == nil {
    verifiers := make(map[string]func(string) bool, len(cfg.Users))
    for u, hpw := range cfg.Users {
        v, err := parseHashedPassword(hpw)
        if err != nil {
            panic(err)
        }
        verifiers[u] = v
    }
    cfg.Authorizer = func(user, pass string, _ fiber.Ctx) bool {
        verify, ok := verifiers[user]
        return ok && verify(pass)   // line 137: short-circuit skips verify() if user unknown
    }
}

Data Flow

1. Attacker sends Authorization: Basic <base64(candidate:wrongpass)>
2. BasicAuth middleware decodes credentials and calls cfg.Authorizer(user, pass, c)
3. Map lookup verifiers[user] returns ok=false for non-existent users
4. Go && short-circuit: false && verify(pass) returns immediately without calling verify()
5. For valid users, verify(pass) executes bcrypt.CompareHashAndPassword() (line 167: ~100ms at default cost 10)
6. Timing difference: ~100ns (invalid user) vs ~100ms (valid user) = 1,000,000:1 ratio

Timing comparison by hash type:

Notes

• Password hash comparisons themselves are timing-safe: subtle.ConstantTimeCompare is used correctly for SHA-256 (line 185), SHA-512 (line 176), and bcrypt uses its own constant-time comparison
• The fix is to always execute a dummy hash comparison for unknown users: bcrypt.CompareHashAndPassword(dummyHash, []byte(pass)) and discard the result
• This pattern matches CVE-2023-36456 (Authentik timing oracle) and similar findings in other auth libraries

• Username enumeration: Attacker reliably determines which usernames exist by measuring response latency
• Targeted brute force: After enumerating valid usernames, password brute force is focused only on real accounts
• Account discovery: In applications where usernames are sensitive (internal tools, admin panels), leaking their existence is itself a security issue

CVE-2026-44332 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.3.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-44332? CVE-2026-44332 is a medium-severity security vulnerability in github.com/gofiber/fiber/v3 (go), affecting versions <= 3.2.0. It is fixed in 3.3.0.
2. How severe is CVE-2026-44332? CVE-2026-44332 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/gofiber/fiber/v3 are affected by CVE-2026-44332? github.com/gofiber/fiber/v3 (go) versions <= 3.2.0 is affected.
4. Is there a fix for CVE-2026-44332? Yes. CVE-2026-44332 is fixed in 3.3.0. Upgrade to this version or later.
5. Is CVE-2026-44332 exploitable, and should I be worried? Whether CVE-2026-44332 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-44332 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-44332? Upgrade github.com/gofiber/fiber/v3 to 3.3.0 or later.