UndiciApplication · Node.js
CVE-2026-16729
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedundici's setCookie function does not fully sanitize cookie attributes. In undici before 6.28.0, from 7.0.0 up to before 7.29.0, and from 8.0.0 up to before 8.9.0, a domain value is not checked for semicolons and entries in the unparsed array are not sanitized, so attacker-influenced input can inject additional cookie attributes. For example, a domain value containing a semicolon can append attributes such as SameSite, and an unparsed entry can inject attributes such as HttpOnly, without the caller setting them. Applications that pass user-controlled input to these fields, such as multi-tenant or reverse-proxy servers that scope session cookies to a tenant-supplied domain, can have SameSite CSRF protections bypassed, or the Secure, HttpOnly, and SameSite attributes forced, stripped, or overridden. The issue is fixed in undici 6.28.0, 7.29.0, and 8.9.0.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysisUntrusted input crosses into a downstream interpreter — SQL, a shell, an HTML page, an LDAP query — without being kept separate from the commands around it, so the attacker's data is read as instructions. This is the parent class behind SQL injection, cross-site scripting, and command injection alike. The durable fix is the same everywhere: keep data and code apart at every boundary, using parameterisation or context-aware encoding rather than building interpreted strings by concatenation.
General guidance for the injection class — the official description and references above are authoritative for this specific CVE. Want a bespoke review and a reviewed fix? Ask our team →
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
UndiciApplication
< 6.28.0>= 7.0.0, < 7.29.0>= 8.0.0, < 8.9.0CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- Low
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped6.28.07.29.08.9.0
undici: 6.28.0 (for v5.x/6.x users), 7.29.0 (for v7.x users), or 8.9.0 (for v8.x users)
- Identify the currently installed undici version by running `npm list undici` or checking package.json
- If using undici version 5.x or 6.x (less than 6.28.0), upgrade to version 6.28.0 by running: `npm install undici@^6.28.0`
- If using undici version 7.x (7.0.0 to before 7.29.0), upgrade to version 7.29.0 by running: `npm install undici@^7.29.0`
- If using undici version 8.x (8.0.0 to before 8.9.0), upgrade to version 8.9.0 by running: `npm install undici@^8.9.0`
- After upgrading, verify the new version is installed: `npm list undici`
- Test the application to ensure cookie handling still works as expected, particularly any setCookie functionality
Generated from the published advisory — verify against the referenced sources before acting.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-16729 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2026-16729 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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