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Review reviewHigh

CVE-2026-12151

undici undici, Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10

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-con...

CVSS
7.5
EPSS
0.79%
52.7% percentile
CISA KEV
Not listed
Published
2026.06.18
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.79%
Technical severityCVSS 7.5

Vulnerability overview

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-con...

Affected product and versions

Product
undici undici, Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10
Affected versions
< 6.26.0, >= 7.0.0 < 7.28.0, >= 8.0.0 < 8.5.0, >= 6.17.0 < 6.27.0
Fixed versions
6.27.0, 7.28.0, 8.5.0

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that undici undici, Cryostat 4 on RHEL 9, Red Hat Enterprise Linux 10 and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
CWE-400, CWE-770