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High 7.5Published Jun 17, 2026

CVE-2026-12151undici WebSocket client vulnerable to denial of service via fragment count bypass

Updated under an hour ago ()

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It affects undici and 16 other products. Add what you run to find out whether that includes you.

No exploitation reported and no EPSS estimate yet.

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Impact: The undici WebSocket client enforces maxPayloadSize on the cumulative byte count of fragments in a message but does not enforce a limit on the number of fragments. A malicious WebSocket server can stream many small or empty continuation frames that each pass per-frame and cumulative-size validation, collectively causing unbounded memory growth in the client process. The result is memory exhaustion and a denial of service. Affected applications are those using the undici WebSocket client (new WebSocket(...)) or the WebSocketStream API that can be induced to connect to an attacker-controlled or compromised WebSocket endpoint. All releases starting at undici 6.17.0 are affected. Patches: Upgrade to undici >= 6.26.0, >= 7.28.0, or >= 8.5.0. Workarounds: No workaround is available. The fix must be applied through an upgrade.

CVSS
7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness (CWE)
CWE-400, CWE-770
Known exploited
Not in CISA's KEV catalog
EPSS (exploitation in the next 30 days)
Not loaded for this CVE
Assigned by
openjs
NVD analysis
Modified
Record last updated
Sep 11, 2026
First seen by InfoSec Signals
Oct 9, 2026

Affected products

Affected products
undici undici
undici:undici (from the name)
before 6.26.0; 6.26.0 not affected; from 7.0.0 before 7.28.0; 7.28.0 not affected; from 8.0.0 before 8.5.0; 8.5.0 not affected
CNA record
from 4.2.0-13 not affected
CISA ADP
7.13
CISA ADP
from 1:24.18.0-1.el10_2 not affected
CISA ADP
from 1:22.23.1-2.el10_0 not affected
CISA ADP
from 9060020260804140259.rhel9 not affected
CISA ADP
Red Hat Cluster Observability Operator 1.5.0
redhat:cluster_observability_operator
from 1782840519 not affected
CISA ADP
from 1783448184 not affected
CISA ADP
from 26.5.0-1.3.hum1 not affected
CISA ADP
from 1787801527 not affected
CISA ADP
from 1783306396 not affected
CISA ADP
Red Hat Red Hat Openshift Data Foundation 4.18
redhat:openshift_data_foundation
from 1786705347 not affected
CISA ADP
from 1782498792 not affected
CISA ADP
Red Hat OpenShift Pipelines
redhat:openshift_pipelines
1
CISA ADP
1
CISA ADP
2
CISA ADP
nodejs undici
nodejs:undici
from 6.17.0 before 6.27.0; from 7.0.0 before 7.28.0; from 8.0.0 before 8.5.0
NVD

References

  • vendor-advisory
  • vendor-advisory

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.

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