CVE-2026-6733: Impact: Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets

Q: How do I fix CVE-2026-6733?

undici: upgrade to 6.27.0, 7.28.0, 8.5.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-6733 being exploited?

CVE-2026-6733 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-2026-6733 affect?

CVE-2026-6733 affects undici. Severity is low (CVSS 3.7). Impact: Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets. An attacker-controlled upstream server can inject an unsolicited HTTP/1.1 response onto an idle socket after a request completes. When

Q: How urgent is CVE-2026-6733?

Priority 21/100. Remotely exploitable, no login, no user action

Routine

LOW 3.7REMOTEUPGRADE

CVE-2026-6733 is a low-severity flaw (CVSS 3.7) affecting undici. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Impact: Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets. An attacker-controlled upstream server can inject an unsolicited HTTP/1.1 response onto an idle socket after a request completes. When the client dispatches the next request on that socket, it associates the injected response with the new request, causing responses to be delivered to the wrong requests. This requires an attacker-controlled or

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	3.7 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 88%)
CISA exploited list	No
Weakness	CWE-367
Published	2026-06-17
Last modified	2026-06-27

Publisher (CNA): openjs · Vendor: nodejs

Last updated 2026-06-27 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-17 18:18 UTCPublished CVE record published
2026-06-27 23:46 UTCUpdated Record last modified

nodejs undici UPGRADE

Affected: < 6.27.0 · >= 7.0.0 and < 7.28.0 · >= 8.0.0 and < 8.5.0

Fixed in: 6.27.0, 7.28.0, 8.5.0

Safe to downgrade to: a release before 7.0.0

1. Check installed version

npm ls undici

2. UPGRADE to 6.27.0

npm install undici@">=6.27.0"

3. If no update is available yet, DOWNGRADE to a release before 7.0.0

npm view undici versions npm install undici@"<7.0.0"

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-2026-6733?

undici: upgrade to 6.27.0, 7.28.0, 8.5.0. Exact commands for each OS are on this page.

Is CVE-2026-6733 being exploited?

CVE-2026-6733 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-2026-6733 affect?

CVE-2026-6733 affects undici. Severity is low (CVSS 3.7). Impact: Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets. An attacker-controlled upstream server can inject an unsolicited HTTP/1.1 response onto an idle socket after a request completes. When

How urgent is CVE-2026-6733?

Priority 21/100. 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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