Description
undici is an HTTP client library for Node.js. In versions 5.15.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its WebSocket client, including the bundled WebSocket exposed by Node.js, can be driven to exhaust process memory by a malicious or compromised WebSocket server. For every PING frame received, the client automatically writes a PONG response and ignores the backpressure signal from the socket write, so a server that streams small PING frames while never reading the client's PONGs makes the outbound write queue and heap grow without bound until the Node.js process runs out of memory and terminates. The attack is remote and unauthenticated, needs only a normal WebSocket connection, and is asymmetric, since small inbound PINGs produce a much larger retained outbound queue, with availability the only impact. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, which pause WebSocket frame parsing when the automatic PONG response hits socket backpressure and resume on drain, bounding the outbound queue, and users should upgrade to one of those versions or later. There is no workaround.
Published: 2026-10-15
Score: 5.9 Medium
EPSS: < 1% Very Low
KEV: No
Impact: Denial of Service (availability)
Action: Patch
AI Analysis

Impact

The vulnerability exists in the WebSocket client of undici, where each PING frame automatically triggers a PONG write that does not respect backpressure, causing an unbounded buildup of data in the outbound write queue and heap memory. This uncontrolled resource consumption can eventually exhaust the Node.js process, leading to a denial of service. The flaw stems from uncontrolled resource consumption (CWE‑400), mismanagement of resource limits (CWE‑405), and unbounded memory allocation (CWE‑770).

Affected Systems

Affected are undici:undici library versions 5.15.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, as well as the bundled WebSocket client exposed by Node.js. Any application utilizing these versions of undici may be impacted.

Risk and Exploitability

With a CVSS score of 5.9, the vulnerability is classified as medium severity, yet the exploit conditions are simple: an attacker only needs to connect via a standard WebSocket to a vulnerable server. This remote, unauthenticated attack can cause memory exhaustion and process termination, disrupting availability. The EPSS score is not available, and the vulnerability is not listed in CISA KEV, the lack of those metrics does not reduce the potential impact. The attack vector is remote and requires no credentials, making it accessible to any entity able to establish a WebSocket connection.

Generated by OpenCVE AI on October 16, 2026 at 06:38 UTC.

Remediation

No solution or workaround provided in the CVE record.

OpenCVE Recommended Actions

  • Upgrade undici to version 6.29.1, 7.30.1, 8.12.2, or later.
  • Restart affected Node.js processes to apply the library update.
  • Add monitoring for memory usage and sudden process restarts as a precaution until the issue is fully resolved.

Generated by OpenCVE AI on October 16, 2026 at 06:38 UTC.

Tracking

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Advisories
Source ID Title
Github GHSA Github GHSA GHSA-9fm3-97px-rjf6 undici WebSocket client vulnerable to Denial of Service via unbounded automatic PONG buffering
History

Fri, 23 Oct 2026 13:30:00 +0000

Type Values Removed Values Added
First Time appeared Undici
Undici undici
Vendors & Products Undici
Undici undici

Mon, 19 Oct 2026 21:00:00 +0000

Type Values Removed Values Added
First Time appeared Nodejs
Nodejs undici
CPEs cpe:2.3:a:nodejs:undici:*:*:*:*:*:node.js:*:*
Vendors & Products Nodejs
Nodejs undici

Fri, 16 Oct 2026 20:30:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Fri, 16 Oct 2026 00:30:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

 threat_severity

Moderate

Thu, 15 Oct 2026 19:00:00 +0000

Type Values Removed Values Added
Description undici is an HTTP client library for Node.js. In versions 5.15.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its WebSocket client, including the bundled WebSocket exposed by Node.js, can be driven to exhaust process memory by a malicious or compromised WebSocket server. For every PING frame received, the client automatically writes a PONG response and ignores the backpressure signal from the socket write, so a server that streams small PING frames while never reading the client's PONGs makes the outbound write queue and heap grow without bound until the Node.js process runs out of memory and terminates. The attack is remote and unauthenticated, needs only a normal WebSocket connection, and is asymmetric, since small inbound PINGs produce a much larger retained outbound queue, with availability the only impact. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, which pause WebSocket frame parsing when the automatic PONG response hits socket backpressure and resume on drain, bounding the outbound queue, and users should upgrade to one of those versions or later. There is no workaround.
Title undici WebSocket client vulnerable to Denial of Service via unbounded automatic PONG buffering
Weaknesses CWE-400
CWE-405
CWE-770
References
Metrics cvssV3_1

{'score': 5.9, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H'}

Subscriptions

Nodejs Undici
Undici Undici
cve-icon MITRE

Status: PUBLISHED

Assigner: openjs

Published:

Updated: 2026-10-16T20:00:38.791Z

Reserved: 2026-10-13T11:00:00.833Z

Link: CVE-2026-109932

cve-icon Vulnrichment

Updated: 2026-10-16T20:00:28.445Z

cve-icon NVD

Status : Analyzed

Published: 2026-10-15T19:17:22.300

Modified: 2026-10-19T20:44:42.247

Link: CVE-2026-109932

cve-icon Redhat

Severity : Moderate

Publid Date: 2026-10-15T18:44:22Z

Links: CVE-2026-109932 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2026-10-23T13:15:14Z

Weaknesses
  • CWE-400

    Uncontrolled Resource Consumption

  • CWE-405

    Asymmetric Resource Consumption (Amplification)

  • CWE-770

    Allocation of Resources Without Limits or Throttling