CyberSecBulletin
CVE-2026-1526NVD status: Modified

undici: Improper Handling of Highly Compressed Data (Data Amplification)

Published Updated By the CyberSecBulletin desk

CVE-2026-1526 is a high-severity improper handling of highly compressed data (data amplification) vulnerability in undici, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected undici versions: < 6.24.0; 7.0.0 < 7.24.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 1.28% chance of exploitation within 30 days, higher than 70% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of undici you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on cna.openjsf.org for workarounds and exact fixed builds.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Undiciundici< 6.24.0; 7.0.0 < 7.24.0Not stated
Red HatCryostat 4 on RHEL 9Not specified in the recordNot stated
Red HatRed Hat Enterprise Linux 10Not specified in the recordNot stated
Red HatRed Hat Enterprise Linux 10.0 Extended Update SupportNot specified in the recordNot stated
Red HatRed Hat Enterprise Linux 8Not specified in the recordNot stated
Red HatRed Hat Enterprise Linux 9Not specified in the recordNot stated
Red HatRed Hat Enterprise Linux 9.6 Extended Update SupportNot specified in the recordNot stated
Red HatCluster Observability Operator 1.5.0Not specified in the recordNot stated
Red HatRed Hat Developer Hub 1.8Not specified in the recordNot stated
Red HatRed Hat Developer Hub 1.9Not specified in the recordNot stated
Red HatRed Hat OpenShift AI 2.16Not specified in the recordNot stated
Red HatRed Hat Openshift Data Foundation 4.18Not specified in the recordNot stated
Red HatRed Hat OpenShift Dev Spaces 3.28Not specified in the recordNot stated
Red HatRed Hat OpenShift Pipelines 1.2Not specified in the recordNot stated
Red HatOpenShift LightspeedNot specified in the recordNot stated
Red HatOpenShift PipelinesNot specified in the recordNot stated
Red HatRed Hat Developer HubNot specified in the recordNot stated
Red HatRed Hat JBoss Enterprise Application Platform 8Not specified in the recordNot stated
Red HatRed Hat JBoss Enterprise Application Platform Expansion PackNot specified in the recordNot stated
Red HatRed Hat OpenShift AI (RHOAI)Not specified in the recordNot stated
Red HatRed Hat OpenShift Dev SpacesNot specified in the recordNot stated
Red HatSelf-service automation portal 2Not specified in the recordNot stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
NoneNothing can be modified.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA.

Scoring systemScoreSeverityScored by
CVSS 3.17.5HighCNA
CVSS 3.17.5HighCNA

Official 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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Handling of Highly Compressed Data (Data Amplification)

The product does not handle or incorrectly handles a compressed input with a very high compression ratio that produces a large output.

More Improper Handling of Highly Compressed Data (Data Amplification) vulnerabilities (CWE-409)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Other vulnerabilities in undici

All undici vulnerabilities

Recent Improper Handling of Highly Compressed Data (Data Amplification) vulnerabilities

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