CVE
Node.js is vulnerable to a client certificate authentication bypass via TLS 1.2 renegotiation servername change
- Exploited
- No known exploitation
- Fix
- Fixed in 22.23.5, 24.22.3, 26.13.1
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. The client changes the servername during a TLS 1.2 renegotiation. The server applies different client-certificate policies per hostname.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 33/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
A client certificate authentication bypass in Node.js TLS lets a remote client with valid credentials for one permitted host renegotiate a TLS 1.2 connection under a different servername. This carries the client's existing authentication to a protected host and bypasses its stricter client-certificate policy, but it only matters on servers that apply different client-certificate rules per hostname.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
A client certificate authentication bypass in Node.js TLS lets a client change the servername during TLS 1.2 renegotiation to reach endpoints it was not authorized for. On a server that applies different client-certificate policies per hostname, for example stricter admin-only client-cert auth on one host and ordinary client-cert auth on another, a client that authenticates for a permitted host can renegotiate the TLS 1.2 connection under a different servername and carry its existing authentication to the protected host, bypassing the stricter policy. This vulnerability affects Node.js 26.x, 24.x, and 22.x.
Who should check
Teams running Node.js 22.x, 24.x or 26.x TLS servers that apply different client-certificate policies per hostname.
Read the source excerpt
“This vulnerability affects all users in active release lines: 22.x, 24.x, 26.x”
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure8/25Specific setups only, reachable over the network
- Reach17/20Affects Node.js (a widely deployed server, runtime, framework or database)
- Severity8.1/10CVSS 8.1
- No patch0/5No signal
What would change the score
- Would score about 83 if added to CISA KEV
- Would score about 78 if CISA's SSVC rates exploitation active
- Would score about 40 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
The client changes the servername during a TLS 1.2 renegotiation. The server applies different client-certificate policies per hostname.Upgrade to a fixed version: 22.23.5, 24.22.3, 26.13.1.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-123872 (Node.js is vulnerable to a client certificate authentication bypass via TLS 1.2 renegotiation servername change), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-123872 (entry last updated 2026-11-11):
Affected:
- nodejs node: from 0.0.0, fixed in 22.23.5; from 23.0.0, fixed in 24.22.3; from 25.0.0, fixed in 26.13.1
Fixed versions: 22.23.5, 24.22.3, 26.13.1.
Conditions (all must be true for the bug to be hit):
- The client changes the servername during a TLS 1.2 renegotiation. (source: https://nodejs.org/en/blog/vulnerability/november-2026-security-releases)
- The server applies different client-certificate policies per hostname. (source: https://nodejs.org/en/blog/vulnerability/november-2026-security-releases)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, low-privilege login, no user action.
CISA KEV: CVE-2026-123872 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-123872 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://nodejs.org/en/blog/vulnerability/november-2026-security-releases
- https://cna.openjsf.org/security-advisories.html
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-123872
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-123872"}.Timeline
- CVE published
- First seen by cve.now
- Posted on X by cve.now
Affected versions
- nodejs node
From 0.0.0 · fixed in 22.23.5; From 23.0.0 · fixed in 24.22.3; From 25.0.0 · fixed in 26.13.1
Evidence 4
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Other links · 1
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-123872
Is CVE-2026-123872 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
When a client changes the servername during a TLS 1.2 renegotiation, a Node.js server can accept a client certificate that was issued for a permitted host and let that client reach endpoints on another host that has a stricter client-certificate policy. The client is authorized for one host but gets through on the other.Source: nodejs.org
Which versions are affected by CVE-2026-123872?
node: from 0.0.0 before 22.23.5; from 23.0.0 before 24.22.3; from 25.0.0 before 26.13.1.Source: cve.now feed data
Am I affected, and how do I check?
Node.js versions before 22.23.5, from 23.0.0 before 24.22.3, and from 25.0.0 before 26.13.1 are in the affected ranges. The setup also needs a server that applies different client-certificate policies per hostname. Check your version with the node --version command and review whether your server sets client-certificate rules for more than one hostname.Source: nodejs.org
How do I fix CVE-2026-123872?
Upgrade to Node.js 22.23.5, 24.22.3, or 26.13.1, depending on the release line you run. Those versions are listed as the fixed releases for the affected ranges.Source: nodejs.org