Skip to content
Noroxi
NVD / CVE Program· CNA openjs

CVE-2026-18540: undici vulnerable to downstream response splitting via retry interceptor

Noroxi assessment

Priority: Monitor (action score 14/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.30% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: undici undici 6.28.1, 7.29.1, 8.10.2; azl3 nodejs 24.21.0-1 on Azure Linux 3.0 24.22.0-1.

Low priority for now. Upgrade to undici undici 6.28.1, 7.29.1, 8.10.2; azl3 nodejs 24.21.0-1 on Azure Linux 3.0 24.22.0-1 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

undici's retry interceptor can append the body of a ranged retry response to bytes already delivered from an earlier partial response while still presenting the original response's status and headers. This happens when an upstream server delivers part of a body without a trustworthy resume checkpoint, for example a non-success response whose headers were already sent or a partial-content response with an unusable content range, then closes the connection and answers the resumed range request with more bytes. As a result the response body can be longer than the Content-Length that the application observes. An application that relays such a response to a downstream HTTP/1.1 peer without normalizing the framing can emit a body that exceeds the forwarded Content-Length, and the excess bytes can be interpreted as the start of a following response, which enables downstream response splitting or desynchronization. Exploitation requires an attacker-controlled upstream server and an application that forwards the response through a framing-sensitive path. This affects undici versions before 6.28.1, from 7.0.0 up to 7.29.1, and from 8.0.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.

LowCVSS 3.7 · v3.1—No exploit Fix available
Published
Sep 4, 2026
Updated
Sep 16, 2026
EPSS
0.3% · 23th percentile

Report tools

JSON

Action score

14

Monitor

Low priority for now.

CVSS
14 / 40 · 3.7 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · openjs
3.7
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-18540

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for nodejs records

Running WordPress? Scan your site free with WP Lens

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

We use this product, ask for help

Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
nodejsundici

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • nodejs undicibefore 6.28.1
  • nodejs undici7.0.0 and later · before 7.29.1
  • nodejs undici8.0.0 and later · before 8.10.2

Versions reported by the vendor

Affected version ranges reported by the assigning authority (openjs). Independent of NVD's CPE analysis and usually ahead of it.

  • undici undici

    • 6.28.1, 7.29.1, 8.10.2not affected
    • before 6.28.1affected · semver
    • 7.0.0 and later · before 7.29.1affected · semver
    • 8.0.0 and later · before 8.10.2affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12node-undicifrom 0—
Debian:14node-undicibefore 8.10.2+dfsg+~cs3.2.2-18.10.2+dfsg+~cs3.2.2-1
npmundicifrom 7.0.0 · before 7.29.17.29.1
npmundicifrom 8.0.0 · before 8.10.28.10.2
npmundicibefore 6.28.16.28.1
Red Hat:hummingbird:1grafana12.4before 0:12.4.10-0.2.hum10:12.4.10-0.2.hum1
Red Hat:hummingbird:1nodejs24before 0:24.21.0-1.hum10:24.21.0-1.hum1
Red Hat:hummingbird:1nodejs24-binbefore 0:24.21.0-1.hum10:24.21.0-1.hum1
Red Hat:hummingbird:1nodejs24-develbefore 0:24.21.0-1.hum10:24.21.0-1.hum1
Red Hat:hummingbird:1nodejs24-docsbefore 0:24.21.0-1.hum10:24.21.0-1.hum1
Red Hat:hummingbird:1nodejs24-full-i18nbefore 0:24.21.0-1.hum10:24.21.0-1.hum1
Red Hat:hummingbird:1nodejs24-libsbefore 0:24.21.0-1.hum10:24.21.0-1.hum1
Red Hat:hummingbird:1nodejs24-npmbefore 0:11.19.0-1.24.21.0.1.hum10:11.19.0-1.24.21.0.1.hum1
Red Hat:hummingbird:1nodejs24-npm-binbefore 0:11.19.0-1.24.21.0.1.hum10:11.19.0-1.24.21.0.1.hum1
Red Hat:hummingbird:1nodejs26before 0:26.8.2-0.1.hum10:26.8.2-0.1.hum1
Red Hat:hummingbird:1nodejs26-binbefore 0:26.8.2-0.1.hum10:26.8.2-0.1.hum1
Red Hat:hummingbird:1nodejs26-develbefore 0:26.8.2-0.1.hum10:26.8.2-0.1.hum1
Red Hat:hummingbird:1nodejs26-docsbefore 0:26.8.2-0.1.hum10:26.8.2-0.1.hum1
Red Hat:hummingbird:1nodejs26-full-i18nbefore 0:26.8.2-0.1.hum10:26.8.2-0.1.hum1
Red Hat:hummingbird:1nodejs26-libsbefore 0:26.8.2-0.1.hum10:26.8.2-0.1.hum1
Red Hat:hummingbird:1nodejs26-npmbefore 0:11.19.1-1.26.8.2.0.1.hum10:11.19.1-1.26.8.2.0.1.hum1
Red Hat:hummingbird:1nodejs26-npm-binbefore 0:26.8.2-0.1.hum10:26.8.2-0.1.hum1

Same product

nodejs: all records

Other highest-scoring records for the same primary product.

  • CVE-2022-35949`undici.request` vulnerable to SSRF using absolute URL on `pathname`
    40Plan
  • CVE-2026-1525undici is vulnerable to Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
    39Monitor
  • CVE-2026-109829undici vulnerable to cache poisoning and cross-user disclosure via cross-origin redirects
    36Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2026-85152Sep 4, 2026 · undici vulnerable to cross-origin cache poisoning via missing origin isolation in interceptors
    29Monitor
  • ← EarlierCVE-2026-18149Sep 4, 2026 · undici vulnerable to Denial of Service via orphaned RetryHandler response body
    23Monitor
  • Later →CVE-2026-19534Sep 4, 2026 · undici vulnerable to Denial of Service via unrequested WebSocket subprotocol
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
undici undici6.28.1Vendor (CNA)
undici undici7.29.1Vendor (CNA)
undici undici8.10.2Vendor (CNA)
azl3 nodejs 24.18.1-1 on Azure Linux 3.0—Microsoft (MSRC)
azl3 nodejs 24.20.0-1 on Azure Linux 3.0—Microsoft (MSRC)
azl3 nodejs 24.21.0-1 on Azure Linux 3.024.22.0-1 · Release NotesMicrosoft (MSRC)
debian:node-undici8.10.2+dfsg+~cs3.2.2-1 · Debian:14Package registry (OSV)
npm:undici6.28.1Package registry (OSV)
npm:undici7.29.1Package registry (OSV)
npm:undici8.10.2Package registry (OSV)
red hat:grafana12.40:12.4.10-0.2.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs240:24.21.0-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs24-bin0:24.21.0-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs24-devel0:24.21.0-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs24-docs0:24.21.0-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs24-full-i18n0:24.21.0-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs24-libs0:24.21.0-1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs24-npm0:11.19.0-1.24.21.0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs24-npm-bin0:11.19.0-1.24.21.0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs260:26.8.2-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-bin0:26.8.2-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-devel0:26.8.2-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-docs0:26.8.2-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-full-i18n0:26.8.2-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-libs0:26.8.2-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-npm0:11.19.1-1.26.8.2.0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-npm-bin0:26.8.2-0.1.hum1 · Red Hat:hummingbird:1Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-1525176 days apartundici is vulnerable to Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
    39Monitor
  • CVE-2026-1672837 days apartundici vulnerable to downstream response desynchronization via retry interceptor
    26Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
none
Integrity
low · data or configuration can be modified
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
Low
Availability impact
None

Weakness class (CWE)

CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (1 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records