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Findings

Vulnerability · CVE-2026-1526

The undici WebSocket client is vulnerable to a denial-of-service attack via unbounded memory consumption during permessage-deflate decompression.

Published Mar 12, 2026 · corrected/updated Sep 4, 2026 · Red Hat undici · evidence confidence high

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.

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2026-1526 is a high public vulnerability record for Red Hat undici. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether Red Hat undici is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: nodejs/undici. Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: CVSS 7.5, EPSS 1.2%. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-409, CWE-770. Sources contributing to this record: csaf, cve_org, epss, nvd. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Exploitation and remediation

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in CISA KEV or VulnCheck KEV.

  • Patch and remediation

    No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Mar 12, 2026 · NIST NVD

    Detected

    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 "deco

  2. Sep 4, 2026 · NIST NVD

    Updated

    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 "deco

Affected

  • cpe nodejs/undiciversion unspecified

Sources

  • CSAF AdvisoriesVendor advisoryRHSA-2026:9742:CVE-2026-1526

    A flaw was found in undici. A remote attacker can exploit this vulnerability by sending a specially crafted compressed frame, known as a "decompression bomb," during permessage-deflate decompression. The undici WebSocket client does not properly limit the size of decompressed dat

    security.access.redhat.com
  • CVE.orgVulnerability recordCVE-2026-1526

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-1526

    30-day exploitation probability 1.2%

    first.org
  • NIST NVDVulnerability recordCVE-2026-1526

    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 en

    nvd.nist.gov

References