High severity · published Jun 17, 2026
CVE-2026-12151
undici WebSocket client vulnerable to denial of service via fragment count bypass
7.5
CVSS
0.8%
EPSS
No
On KEV
Description
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.8% · higher than 56% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
UN
undici · undici
before 6.26.0; 7.0.0 before 7.28.0; 8.0.0 before 8.5.0 · source: vendor, NVD
CO
Cluster Observability Operator 1.5.0 · Red Hat
All versions, or not specified · source: CISA
C4
Cryostat 4 on RHEL 9 · Red Hat
All versions, or not specified · source: CISA
OP
OpenShift Pipelines · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Build of Podman Desktop · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Developer Hub 1.10 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Developer Hub 1.9 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 10 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 10.0 Extended Update Support · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 8 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 9 · Red Hat
All versions, or not specified · source: CISA
RH
Red Hat Enterprise Linux 9.6 Extended Update Support · Red Hat
All versions, or not specified · source: CISA
Affected product
UN
undici
undici
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