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

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.

Published: 2026-06-17 Last update: 2026-06-29 Assigner: ce714d77-add3-4f53-aff5-83d477b104bb Source: ce714d77-add3-4f53-aff5-83d477b104bb
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-12151 is rated Moderate Risk (45.1/100): CVSS High severity, with low exploitation likelihood (EPSS 0.57%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-12151

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-30 0.46% 0.57% +0.11%
2 2026-06-27 0.43% 0.46% +0.03%
3 2026-06-23 — 0.43% —

Full EPSS history (4 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-12151

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 ce714d77-add3-4f53-aff5-83d477b104bb
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 0b0ca135-0b70-47e7-9f44-1890c2a1c46c

Weakness enumeration for CVE-2026-12151

GitHub Security Advisory for CVE-2026-12151

GHSA-vxpw-j846-p89q · Severity: high · Ecosystem: npm — undici WebSocket client vulnerable to denial of service via fragment count bypass

OS Trackers for CVE-2026-12151

vendor priority summary link
debian not yet assigned CVE-2026-12151 not yet assigned priority: Debian including 1 source packages (node-undici), 4 status rows across 4 suites (bookworm, forky, sid, trixie): open 2, resolved 2. https://security-tracker.debian.org/tracker/CVE-2026-12151
redhat high — https://access.redhat.com/security/cve/CVE-2026-12151
suse medium CVE-2026-12151 severity moderate: SUSE including 24 source package names (nodejs10, nodejs10-devel, …), 79 product×package rows across 12 product lines (SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS, SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS, … (12 product lines)): Known Not Affected 79. https://www.suse.com/security/cve/CVE-2026-12151/
ubuntu medium CVE-2026-12151 medium priority: Ubuntu including 1 source packages (node-undici), 5 status rows across 5 suites (jammy, noble, questing, resolute, upstream): needs-triage 4, DNE 1. https://ubuntu.com/security/CVE-2026-12151

Affected software / configurations for CVE-2026-12151

Vendor Product Version Raw CPE
nodejs undici >= 6.17.0, < 6.27.0 cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:*
nodejs undici >= 7.0.0, < 7.28.0 cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:*
nodejs undici >= 8.0.0, < 8.5.0 cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:*

References for CVE-2026-12151

cvelogic Threat Intelligence