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Vulnerabilities

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 · catalog updated Sep 4, 2026 · Red Hat

Check if you run it

No confirmed exploitation is on record for CVE-2026-1526. EPSS is 1.17%. Act only if a listed version of Red Hat is installed.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
1.17%
Remediation
Advisory link
Affected products
cpe nodejs/undici

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.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe nodejs/undiciversion unspecified

How to fix CVE-2026-1526

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-1526. EPSS is 1.17%. Act only if a listed version of Red Hat is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-409; CWE-770: Allocation of Resources Without Limits or Throttling. EPSS 1.17%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

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

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

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.