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CVE.org (no NVD analysis yet)· CNA openjs

CVE-2026-109855: undici WebSocket client vulnerable to Denial of Service via failed HTTP/2 handshake

HighCVSS 7.5 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 30/100)

  • 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: 0.27% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • According to CISA the attack is automatable: targets can be found by mass scanning.
  • Fixed version: undici undici 8.11.2.

Low priority for now. Upgrade to undici undici 8.11.2 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 is an HTTP client library for Node.js. In versions 8.11.0 and 8.11.1, its experimental WebSocket client, which is enabled by default when HTTP/2 is allowed, mishandles a failed WebSocket handshake over HTTP/2: the request is already marked completed, so the abort becomes a no-op and the underlying HTTP/2 stream is left open with no error listener. When a malicious server then destroys the connection, the orphaned stream emits an unhandled error and the Node.js process exits. A remote, unauthenticated server can therefore crash any client that opens a WebSocket to it over HTTP/2, resulting in a denial of service. The issue is fixed in undici 8.11.2, and users should upgrade to 8.11.2 or later. As a workaround, set allowH2 to false to disable HTTP/2 for WebSocket connections, or avoid opening WebSocket connections to untrusted servers.

Published
Oct 15, 2026
Updated
Oct 19, 2026
EPSS
0.2% · 20th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · openjs
7.5
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.

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

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Follow CVE-2026-109855

When you'll hear from us

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

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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.

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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

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

    • 8.11.2not affected
    • 8.11.0 and later · before 8.11.2affected · semver

Affected versions

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

  • nodejs undici8.11.0 and later · before 8.11.2

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:14node-undicibefore 8.12.2+dfsg+~cs3.2.3-18.12.2+dfsg+~cs3.2.3-1
npmundicifrom 8.11.0 · before 8.11.28.11.2
Red Hat:hummingbird:1grafana12.4before 0:12.4.12-0.4.hum10:12.4.12-0.4.hum1
Red Hat:hummingbird:1nodejs26before 0:26.11.1-0.3.hum10:26.11.1-0.3.hum1
Red Hat:hummingbird:1nodejs26-binbefore 0:26.11.1-0.3.hum10:26.11.1-0.3.hum1
Red Hat:hummingbird:1nodejs26-develbefore 0:26.11.1-0.3.hum10:26.11.1-0.3.hum1
Red Hat:hummingbird:1nodejs26-docsbefore 0:26.11.1-0.3.hum10:26.11.1-0.3.hum1
Red Hat:hummingbird:1nodejs26-full-i18nbefore 0:26.11.1-0.3.hum10:26.11.1-0.3.hum1
Red Hat:hummingbird:1nodejs26-libsbefore 0:26.11.1-0.3.hum10:26.11.1-0.3.hum1
Red Hat:hummingbird:1nodejs26-npmbefore 0:11.20.0-1.26.11.1.0.3.hum10:11.20.0-1.26.11.1.0.3.hum1
Red Hat:hummingbird:1nodejs26-npm-binbefore 0:26.11.1-0.3.hum10:26.11.1-0.3.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-2026-19534Sep 4, 2026 · undici vulnerable to Denial of Service via unrequested WebSocket subprotocol
    30Monitor
  • ← EarlierCVE-2026-84890Sep 4, 2026 · undici vulnerable to Denial of Service via unbounded decompression of compressed responses
    23Monitor
  • Later →CVE-2026-109383Oct 15, 2026 · undici vulnerable to TLS certificate validation bypass via dropped tls options in Agent
    36Monitor

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 undici8.11.2Vendor (CNA)
debian:node-undici8.12.2+dfsg+~cs3.2.3-1 · Debian:14Package registry (OSV)
npm:undici8.11.2Package registry (OSV)
red hat:grafana12.40:12.4.12-0.4.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs260:26.11.1-0.3.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-bin0:26.11.1-0.3.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-devel0:26.11.1-0.3.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-docs0:26.11.1-0.3.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-full-i18n0:26.11.1-0.3.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-libs0:26.11.1-0.3.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-npm0:11.20.0-1.26.11.1.0.3.hum1 · Red Hat:hummingbird:1Package registry (OSV)
red hat:nodejs26-npm-bin0:26.11.1-0.3.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.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 13, 2026+29 d
EPSS, last 120 days

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

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-2026-1098690 days apartundici vulnerable to Denial of Service via unhandled error on excessive content-encodings
    30Monitor
  • CVE-2026-870180 days apartundici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation
    30Monitor
  • CVE-2026-870290 days apartundici vulnerable to Denial of Service via unhandled exception in the decompress interceptor
    30Monitor
  • CVE-2026-1953441 days apartundici vulnerable to Denial of Service via unrequested WebSocket subprotocol
    30Monitor
  • CVE-2026-8501441 days apartundici vulnerable to Denial of Service via WebSocketStream unclean close
    30Monitor
  • CVE-2026-2229217 days apartundici is vulnerable to Unhandled Exception in undici WebSocket Client Due to Invalid server_max_window_bits Validation
    30Monitor

Bug bounty scope

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

Not on record for this CVE: patch commit or PR link.

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.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-248 · Uncaught Exception

CVSS vector

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

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.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. SSVC exploitation— → none
  2. Exploit maturity— → none
  3. 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