CVE-2026-84961: undici's BalancedPool constructor passes its entire options object through an internal deep-clone that seriali

Q: How do I fix CVE-2026-84961?

undici: upgrade to 7.29.1, 8.10.2. Exact commands for each OS are on this page.

Q: Is CVE-2026-84961 being exploited?

CVE-2026-84961 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-84961 affect?

CVE-2026-84961 affects undici. Severity is high (CVSS 7.4). 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-supp

Q: How urgent is CVE-2026-84961?

Priority 33/100. High severity; Remotely exploitable, no login, no user action

Routine

HIGH 7.4REMOTEUPGRADE

CVE-2026-84961 is a high-severity flaw (CVSS 7.4) affecting undici. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 checkServe

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.4 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 93%)
CISA exploited list	No
Weakness	CWE-295
Published	2026-09-04
Last modified	2026-09-15

Publisher (CNA): openjs · Vendor: nodejs

Last updated 2026-09-15 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-04 17:17 UTCPublished CVE record published
2026-09-15 14:29 UTCUpdated Record last modified

nodejs undici UPGRADE

Affected: >= 7.24.1 and < 7.29.1 · >= 8.0.0 and < 8.10.2

Fixed in: 7.29.1, 8.10.2

Safe to downgrade to: a release before 7.24.1

1. Check installed version

npm ls undici

2. UPGRADE to 7.29.1

npm install undici@">=7.29.1"

3. If no update is available yet, DOWNGRADE to a release before 7.24.1

npm view undici versions npm install undici@"<7.24.1"

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-84961?

undici: upgrade to 7.29.1, 8.10.2. Exact commands for each OS are on this page.

Is CVE-2026-84961 being exploited?

CVE-2026-84961 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-84961 affect?

CVE-2026-84961 affects undici. Severity is high (CVSS 7.4). 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-supp

How urgent is CVE-2026-84961?

Priority 33/100. High severity; Remotely exploitable, no login, no user action

Software pages

Node.js vulnerabilities

Related CVEs

CVE-2026-109855 HIGH 7.5 UPGRADE undici is an HTTP client library for Node.js
CVE-2026-109383 HIGH 7.4 UPGRADE undici is an HTTP client library for Node.js
CVE-2026-109829 HIGH 7.4 UPGRADE undici is an HTTP client library for Node.js
CVE-2026-109841 MEDIUM 5.9 UPGRADE undici is an HTTP client library for Node.js
CVE-2026-109869 HIGH 7.5 UPGRADE undici is an HTTP client library for Node.js

References

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