CVE-2026-1526

undici is vulnerable to Unbounded Memory Consumption in undici WebSocket permessage-deflate Decompression

CVSS 3.1 7.5 HIGHEUVD CVSS 3.1 7.5 CVSS 3.1 · ce714d77-add3-4f53-aff5-83d477b104bb · Secondary 7.5 HIGHCVSS 3.1 · 0b0ca135-0b70-47e7-9f44-1890c2a1c46c · Secondary 7.5 HIGHCVSS_V3 Publisher rating HIGHFixed by undici 6.24.0 Fixed by undici 7.24.0KEV status unknown

Original advisory

cve-program · CVE-2026-1526

Published

The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When a WebSocket connection negotiates the permessage-deflate extension, the client decompresses incoming compressed frames without enforcing any limit on the decompressed data size. A malicious WebSocket server can send a small compressed frame (a "decompression bomb") that expands to an extremely large size in memory, causing the Node.js process to exhaust available memory and crash or become unresponsive. The vulnerability exists in the PerMessageDeflate.decompress() method, which accumulates all decompressed chunks in memory and concatenates them into a single Buffer without checking whether the total size exceeds a safe threshold.

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euvd · EUVD-2026-11699

Published

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nvd · CVE-2026-1526

Published

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osv · GHSA-vrm6-8vpv-qv8q

Published

## Description The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When a WebSocket connection negotiates the permessage-deflate extension, the client decompresses incoming compressed frames without enforcing any limit on the decompressed data size. A malicious WebSocket server can send a small compressed frame (a "decompression bomb") that expands to an extremely large size in memory, causing the Node.js process to exhaust available memory and crash or become unresponsive. The vulnerability exists in the `PerMessageDeflate.decompress()` method, which accumulates all decompressed chunks in memory and concatenates them into a single Buffer without checking whether the total size exceeds a safe threshold. ## Impact - Remote denial of service against any Node.js application using undici's WebSocket client - A single compressed WebSocket frame of ~6 MB can decompress to ~1 GB or more - Memory exhaustion occurs in native/external memory, bypassing V8 heap limits - No application-level mitigation is possible as decompression occurs before message delivery ### Patches Users should upgrade to fixed versions. ### Workarounds No workaround are possible.

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Affected versions, risk and source history

Exploitation and risk

Source status

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cve-program · CVE-2026-1526

Published

undici is vulnerable to Unbounded Memory Consumption in undici WebSocket permessage-deflate Decompression

Source published: 12 Mar 2026 20:08:05 UTC
Source modified: 14 Sep 2026 12:04:31 UTC
Saved here: 23 Oct 2026 15:48:27 UTC
Source terms: CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

euvd · EUVD-2026-11699

Published

The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression. When a WebSocket connection negotiates the permessage-deflate extension, the client decompress…

Additional publisher context

EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON.

Original publisher date fields

datePublished: Mar 12, 2026, 8:08:05 PM

dateUpdated: Sep 14, 2026, 12:04:31 PM

17 related source bulletins · separate from aliases

RHSA-2026:7302: Red Hat Security Advisory: nodejs:22 security update