CVE
sync-rpc: Arbitrary remote code execution vulnerability
sync-rpc versions before 1.3.7 let an attacker who can guess the sync-rpc port and reach it past any firewall run JavaScript files stored on the server. Fixed in 1.3.7.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 1.3.7
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 1.3.7.
- Published
- 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? →
- 26/100 · 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
sync-rpc, from ForbesLindesay, is affected by a flaw that lets an attacker remotely, without logging in, run arbitrary JavaScript files stored on the server running it, provided they can guess the correct port and that port is not blocked by a firewall. The issue is fixed in a newer release.
Read the original description
sync-rpc runs asynchronous commands synchronously by putting them in a separate proces. Prior to version 1.3.7, if an attacker could guess the correct port and it was not blocked via a firewall, it was possible to load and execute arbitrary JavaScript files stored on the server running sync-rpc. This issue has been patched in version 1.3.7.
Who should check
Teams running sync-rpc before 1.3.7, including Node.js services that use it to run asynchronous commands synchronously
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
- Reach?/20Unknown. No tracked technology or package matched
- Severity8.7/10CVSS 8.7
- No patch0/5No signal
What would change the score
- Would score about 71 if added to CISA KEV
- Would score about 66 if CISA's SSVC rates exploitation active
- Would score about 31 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 1.3.7.
Workaround: Use a restrictive firewall that blocks all ports except those actively in use
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-2026-65843 (sync-rpc: Arbitrary remote code execution vulnerability), 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-2026-65843 (entry last updated 2026-11-11):
Affected:
- ForbesLindesay sync-rpc: fixed in 1.3.7
Fixed versions: 1.3.7.
Conditions (all must be true for the bug to be hit):
- Attacker must be able to guess the correct sync-rpc port (source: https://github.com/ForbesLindesay/sync-rpc/security/advisories/GHSA-2x86-cf3f-86gw)
- The port is not blocked by a firewall (source: https://github.com/ForbesLindesay/sync-rpc/security/advisories/GHSA-2x86-cf3f-86gw)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, no login, no user action.
Workaround: Use a restrictive firewall that blocks all ports except those actively in use (source: https://github.com/ForbesLindesay/sync-rpc/security/advisories/GHSA-2x86-cf3f-86gw)
CISA KEV: CVE-2026-65843 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-65843 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://github.com/ForbesLindesay/sync-rpc/security/advisories/GHSA-2x86-cf3f-86gw
- https://github.com/ForbesLindesay/sync-rpc/commit/ffccfe5bc39ad2e291a79c9e5afe6155ad311f07
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-2026-65843
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-2026-65843"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- ForbesLindesay sync-rpc
fixed in 1.3.7
Evidence 4
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Other links · 1
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-65843
Is CVE-2026-65843 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?
sync-rpc runs a network port that accepts requests to load JavaScript files. Because the port could be guessed and was not blocked by a firewall, an attacker could load and execute arbitrary JavaScript files stored on the server running sync-rpc.Source: github.com
Which versions are affected by CVE-2026-65843?
sync-rpc: before 1.3.7.Source: cve.now feed data
Am I affected, and how do I check?
Versions of sync-rpc before 1.3.7 are affected, and the risk depends on the port being guessable and reachable past any firewall. To check a project, look at the sync-rpc version listed in its package.json or installed dependency tree.Source: github.com
How do I fix CVE-2026-65843?
Upgrade sync-rpc to version 1.3.7 or later, which contains the patch.Source: github.com