Vulnerability-Lookup

GHSA-W293-VG96-WGC3

Vulnerability from github – Published: 2026-09-29 18:17 – Updated: 2026-09-29 18:17

Summary

undici vulnerable to TLS certificate validation bypass via dropped connect options in BalancedPool

Details

Impact

undici's BalancedPool passes its constructor options through a JSON-based deep clone (JSON.parse(JSON.stringify(...))) before forwarding them to each per-upstream Pool. JSON cannot represent functions, so a caller-supplied connect or tls option containing a checkServerIdentity callback (or a custom connector function) is silently dropped before it reaches the TLS layer. As a result, a TLS peer whose certificate a custom checkServerIdentity was written to reject, but which passes Node's default hostname and chain checks, is silently accepted when the request is made through BalancedPool. Client, Pool, Agent, and RoundRobinPool destructure connect/tls before the clone and are not affected. Only applications that use BalancedPool with a function-valued connect/tls option (such as a custom checkServerIdentity or connector) are affected.

Patches

Upgrade to 7.29.1 or 8.10.2. BalancedPool now preserves the connect and tls options outside the JSON clone, so custom TLS verification callbacks are forwarded to each upstream unchanged.

Workarounds

Use Client, Pool, or Agent instead of BalancedPool for connections that rely on a custom checkServerIdentity or connector, until upgraded.

Severity

7.4 (High)


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

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{
  "affected": [
    {
      "package": {
        "ecosystem": "npm",
        "name": "undici"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "7.24.1"
            },
            {
              "fixed": "7.29.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "npm",
        "name": "undici"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "8.0.0"
            },
            {
              "fixed": "8.10.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-84961"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-295"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-29T18:17:15Z",
    "nvd_published_at": "2026-09-04T17:17:02Z",
    "severity": "HIGH"
  },
  "details": "### Impact\n\nundici\u0027s `BalancedPool` passes its constructor options through a JSON-based deep clone (`JSON.parse(JSON.stringify(...))`) before forwarding them to each per-upstream `Pool`. JSON cannot represent functions, so a caller-supplied `connect` or `tls` option containing a `checkServerIdentity` callback (or a custom connector function) is silently dropped before it reaches the TLS layer. As a result, a TLS peer whose certificate a custom `checkServerIdentity` was written to reject, but which passes Node\u0027s default hostname and chain checks, is silently accepted when the request is made through `BalancedPool`. `Client`, `Pool`, `Agent`, and `RoundRobinPool` destructure `connect`/`tls` before the clone and are not affected. Only applications that use `BalancedPool` with a function-valued `connect`/`tls` option (such as a custom `checkServerIdentity` or connector) are affected.\n\n### Patches\n\nUpgrade to `7.29.1` or `8.10.2`. `BalancedPool` now preserves the `connect` and `tls` options outside the JSON clone, so custom TLS verification callbacks are forwarded to each upstream unchanged.\n\n### Workarounds\n\nUse `Client`, `Pool`, or `Agent` instead of `BalancedPool` for connections that rely on a custom `checkServerIdentity` or connector, until upgraded.",
  "id": "GHSA-w293-vg96-wgc3",
  "modified": "2026-09-29T18:17:15Z",
  "published": "2026-09-29T18:17:15Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/security/advisories/GHSA-w293-vg96-wgc3"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-84961"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/commit/8f5868fbdbc8f1146dfc1bcd1f2d117790141390"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/commit/f690157d728508652fef14673630c71515123e96"
    },
    {
      "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/v7.29.1"
    },
    {
      "type": "WEB",
      "url": "https://github.com/nodejs/undici/releases/tag/v8.10.2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "undici vulnerable to TLS certificate validation bypass via dropped connect options in BalancedPool"
}

CVE-2026-84961 (GCVE-0-2026-84961)

Vulnerability from cvelistv5 – Published: 2026-09-04 16:47 – Updated: 2026-09-04 18:37

Title

undici vulnerable to TLS certificate validation bypass via dropped connect options in BalancedPool

Summary

undici's BalancedPool constructor passes its entire options object through an internal deep-clone that serializes and reparses the value as JSON. Because JSON cannot represent functions, any function-valued TLS option, such as a caller-supplied checkServerIdentity callback or a custom connector inside the connect option, is silently discarded before it reaches the TLS layer. As a result a peer whose certificate the application's custom checkServerIdentity was written to reject, but which still passes Node's default hostname and chain checks, is accepted when reached through BalancedPool. The Client, Pool, and Agent dispatchers are not affected because they extract the connect and tls options before cloning. This affects undici versions from 7.24.1 up to 7.29.1 and from 8.0.0 up to 8.10.2, and only when the application supplies a function-valued connect or tls option to BalancedPool. Users should upgrade to undici 7.29.1 or 8.10.2.

Severity

7.4 (High)


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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-04 18:35 UTC

CWE

CWE-295 - Improper Certificate Validation

Assigner

openjs redhat root Scorecard

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: 7.24.1 , < 7.29.1 (semver) Unaffected: 7.29.1 (semver) Affected: 8.0.0 , < 8.10.2 (semver) Unaffected: 8.10.2 (semver)

Credits

MegaManSec mcollina UlisesGascon

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JSON

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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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
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