CVE
Node.js is vulnerable to cross-connection memory disclosure via TLS write re-entrancy in the HTTPS request parser
Affects the Node.js HTTPS server on release lines 22.x, 24.x and 26.x; cleartext node:http is not affected. Fixed in 22.23.5, 24.22.3 and 26.13.1.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 22.23.5, 24.22.3, 26.13.1
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 22.23.5, 24.22.3, 26.13.1.
- 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? →
- 42/100 · 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? →
- Unclear
- 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
Node.js HTTPS servers can leak memory from other connections, including TLS private keys and other users' requests, to an unauthenticated remote client. The attacker must send a request to a handler that calls res.flushHeaders() before the request body ends and later calls res.end() with a non-empty chunk, and the leak only works when the server echoes or stores request bodies on an ordinary route; cleartext node:http is not affected.
Read the original description
A re-entrancy flaw in Node.js HTTPS lets an unauthenticated client read memory belonging to other connections, including TLS private keys and other users' requests. TLSWrap::DoWrite() calls ClearOut() directly when asked to write zero bytes; if that write is issued from JavaScript running inside the HTTP parser's on_body callback, ClearOut() decrypts the next TLS record while the parser is still mid-body, re-entering llhttp_execute() and causing a use-after-free and an out-of-bounds heap read. The server then copies that freed or unrelated heap memory into the response for the request body. Triggering it requires a handler that calls res.flushHeaders() before the request body ends and later calls res.end() with a non-empty chunk, and reading the leaked memory requires any ordinary route that echoes or stores a request body. Cleartext node:http is not affected. This vulnerability affects Node.js 26.x, 24.x, and 22.x.
Who should check
Teams running HTTPS servers on Node.js 22.x, 24.x or 26.x whose handlers call res.flushHeaders() and echo or store request bodies.
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
- Exposure17/25No login or user action needed, reachable over the network without a login · Unknown: Advisories don't say whether default setups are affected
- 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 87 if added to CISA KEV
- Would score about 82 if CISA's SSVC rates exploitation active
- Would score about 47 if advisories confirm default setups are exposed
What to do
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-2026-123864 (Node.js is vulnerable to cross-connection memory disclosure via TLS write re-entrancy in the HTTPS request parser), 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-2026-123864 (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):
- Node.js HTTPS server (cleartext node:http is not affected) (source: https://nodejs.org/en/blog/vulnerability/november-2026-security-releases)
- Affected release lines are 22.x, 24.x and 26.x (source: https://nodejs.org/en/blog/vulnerability/november-2026-security-releases)
- A handler calls res.flushHeaders() before the request body ends and later calls res.end() with a non-empty chunk (source: https://nodejs.org/en/blog/vulnerability/november-2026-security-releases)
- A route that echoes or stores a request body (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, no login, no user action.
CISA KEV: CVE-2026-123864 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-123864 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-2026-123864
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-2026-123864"}.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-2026-123864
Is CVE-2026-123864 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?
A flaw in the Node.js HTTPS request parser lets an unauthenticated remote client read memory belonging to other connections, including TLS private keys and other users' requests. The leak is triggered when a handler calls res.flushHeaders() before the request body ends and later calls res.end() with a non-empty chunk.Source: nodejs.org
Which versions are affected by CVE-2026-123864?
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?
Release lines 22.x, 24.x and 26.x of Node.js are affected, but only the HTTPS server; cleartext node:http is not. Check the installed version with node --version. The bug also needs a handler that calls res.flushHeaders() early, and reading the leaked memory needs an ordinary route that echoes or stores a request body.Source: nodejs.org
How do I fix CVE-2026-123864?
Upgrade to 22.23.5 on the 22.x line, 24.22.3 on the 24.x line, or 26.13.1 on the 26.x line, or to a later release in the same line.Source: nodejs.org