5.9

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-22036

CVE-2026-22036: Undici has an unbounded decompression chain in HTTP responses on Node.js Fetch API via Content-Encoding leads to resource exhaustion

Undici is an HTTP/1.1 client for Node.js. Prior to 7.18.0 and 6.23.0, the number of links in the decompression chain is unbounded and the default maxHeaderSize allows a malicious server to insert thousands compression steps leading to high CPU usage and excessive memory allocation. This vulnerability is fixed in 7.18.0 and 6.23.0.

(GitHub Advisory)

Miggo Vulnerability Database

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CVE-2026-22036

CVE-2026-22036:

5.9

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
undici	npm	>= 7.0.0, < 7.18.2	7.18.2
undici	npm	< 6.23.0	6.23.0

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The analysis of the provided patch commit b04e3cbb569c1596f86c108e9b52c79d8475dcb3 directly points to the vulnerable function. The vulnerability, described as an unbounded decompression chain, is addressed in the file lib/interceptor/decompress.js. Specifically, the function DecompressHandler.#createDecompressionChain is modified to add a limit to the number of Content-Encoding parts it will process. Previously, it would split the Content-Encoding header and create a decompressor for each part without any bounds. A malicious server could exploit this by sending a response with a very long list of encodings, leading to resource exhaustion. The patch introduces a hard limit of 5 encodings, throwing an error if this limit is exceeded. The associated test file test/interceptors/decompress.js confirms this by adding test cases that check for an excessive number of encodings. Therefore, DecompressHandler.#createDecompressionChain is the precise function where the vulnerability existed.

Vulnerable functions

DecompressHandler.#createDecompressionChain

lib/interceptor/decompress.js

The vulnerability lies in the `#createDecompressionChain` function within the `DecompressHandler` class. Before the patch, this function did not limit the number of compression algorithms specified in the `Content-Encoding` header. A malicious server could send a response with a header containing a large number of encodings (e.g., 'gzip, gzip, gzip, ...'), causing the application to create a long chain of decompressor streams. This would lead to excessive CPU and memory consumption, resulting in a denial of service. The patch mitigates this by introducing a limit of 5 encodings.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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