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GHSA-4QV8-2P9J-2685

Vulnerability from github – Published: 2026-10-23 22:13 – Updated: 2026-10-23 22:13

Summary

undici vulnerable to Denial of Service via unbounded memory in the EventSource parser

Details

Impact

undici's EventSource client can be driven to exhaust process memory by a malicious or compromised Server-Sent Events peer. By sending millions of tiny completed data: fields with no blank event separator, or a single unfinished line split across many chunks, the parser retains a growing amount of per-field and per-chunk state. The byte-based maxEventSize and maxResponseSize limits do not bound that retained state, and maxResponseSize is enforced on the compressed body before decompression, so a small compressed response can expand into enough retained memory to terminate the process. The application only needs to maintain an EventSource connection to an untrusted peer, which controls only the response. Availability is the only impact.

Patches

Upgrade to 6.29.1, 7.30.1, or 8.12.2, which bound the retained EventSource parser state (the number of data fields and buffered chunks, the unfinished-line length, and per-field byte totals) independently of the byte limits.

Workarounds

None.

Severity

5.9 (Medium)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "undici"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "6.5.0"
            },
            {
              "fixed": "6.29.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "undici"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "7.0.0"
            },
            {
              "fixed": "7.30.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "undici"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "8.0.0"
            },
            {
              "fixed": "8.12.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-109924"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-770"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-10-23T22:13:29Z",
    "nvd_published_at": "2026-10-15T19:17:22Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nundici\u0027s `EventSource` client can be driven to exhaust process memory by a malicious or compromised Server-Sent Events peer. By sending millions of tiny completed `data:` fields with no blank event separator, or a single unfinished line split across many chunks, the parser retains a growing amount of per-field and per-chunk state. The byte-based `maxEventSize` and `maxResponseSize` limits do not bound that retained state, and `maxResponseSize` is enforced on the compressed body before decompression, so a small compressed response can expand into enough retained memory to terminate the process. The application only needs to maintain an `EventSource` connection to an untrusted peer, which controls only the response. Availability is the only impact.\n\n### Patches\n\nUpgrade to `6.29.1`, `7.30.1`, or `8.12.2`, which bound the retained EventSource parser state (the number of `data` fields and buffered chunks, the unfinished-line length, and per-field byte totals) independently of the byte limits.\n\n### Workarounds\n\nNone.",
  "id": "GHSA-4qv8-2p9j-2685",
  "modified": "2026-10-23T22:13:30Z",
  "published": "2026-10-23T22:13:29Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/security/advisories/GHSA-4qv8-2p9j-2685"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-109924"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/commit/299162740d5f39120092277e70efacb4d151c1c6"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/commit/789ef26461c648480433846607154f52d74ec9ab"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/commit/c43b23fdc6b37e1283d4347408bb16800f867d9e"
    },
    {
      "type": "WEB",
      "url": "https://cna.openjsf.org/security-advisories.html"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/nodejs/undici"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/releases/tag/v6.29.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/releases/tag/v7.30.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/releases/tag/v8.12.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "undici vulnerable to Denial of Service via unbounded memory in the EventSource parser"
}

CVE-2026-109924 (GCVE-0-2026-109924)

Vulnerability from cvelistv5 – Published: 2026-10-15 18:16 – Updated: 2026-10-16 20:05

Title

undici vulnerable to Denial of Service via unbounded memory in the EventSource parser

Summary

undici is an HTTP client library for Node.js. In versions 6.5.0 through 6.29.0, 7.0.0 through 7.30.0, and 8.0.0 through 8.12.1, its EventSource client can be driven to exhaust process memory by a malicious or compromised Server-Sent Events peer. By sending millions of tiny completed data fields with no blank event separator, or a single unfinished line split across many chunks, the parser retains a growing amount of per-field and per-chunk state that the byte-based maxEventSize and maxResponseSize limits do not bound, and because maxResponseSize is enforced on the compressed body before decompression, a small compressed response can expand into enough retained memory to terminate the process. An application only needs to maintain an EventSource connection to an untrusted peer, which controls only the response, and availability is the only impact. The issue is fixed in undici 6.29.1, 7.30.1, and 8.12.2, which bound the retained parser state independently of the byte limits, and users should upgrade to one of those versions or later. There is no workaround.

Severity

5.9 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-16 20:05 UTC

CWE

CWE-770 - Allocation of Resources Without Limits or Throttling

Assigner

openjs CNA under the redhat root

CNA scorecard C 65/100 over 118 records in the last 180 days details

References

2 references

URL	Tags
https://github.com/nodejs/undici/security/advisor…
https://cna.openjsf.org/security-advisories.html

Impacted products

1 product

Vendor	Product	Version
undici	undici	Affected: 6.5.0 , < 6.29.1 (semver) Unaffected: 6.29.1 (semver) Affected: 7.0.0 , < 7.30.1 (semver) Unaffected: 7.30.1 (semver) Affected: 8.0.0 , < 8.12.2 (semver) Unaffected: 8.12.2 (semver)

Credits

iamibi mcollina UlisesGascon KhafraDev

Show details on NVD website

JSON

To clipboard

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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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