● High · CVSS 7.1

How to Fix CVE-2026-23940: Denial of Service via Oversized Package Upload in hexpm

Q: Is CVE-2026-23940 being actively exploited?

Not at the time of writing. It is not listed in CISA's Known Exploited Vulnerabilities catalog. That status can change, so monitor the vendor advisory and the KEV catalog if the system is exposed.

Q: How severe is CVE-2026-23940?

CVSS rates it 7.1 (High). Use that score to set your patch priority next to the other items in your queue.

Q: Do I have to take hexpm offline to apply the patch?

It depends on the deployment. High-availability or clustered installs can usually patch one node at a time with no full outage. Standalone installs typically need a short restart. Always follow the vendor's documented upgrade steps.

Q: What if my vulnerability scanner still flags CVE-2026-23940 after I patch?

Re-run the scan after a service restart, then confirm the scanner's plugin set is up to date. Some scanners detect by banner version only and lag the official fix metadata by a release.

Other vulnerabilities in the same area that are worth patching alongside this one:

How to Fix CVE-2026-2327: Critical Vulnerability in markdown-it — Critical Vulnerability in markdown-it
How to Fix CVE-2026-0711: CWE-78 Improper neutralization of special elements used in an OS command ('OS command injection') — CWE-78 Improper neutralization of special elements used in an OS command ('OS command injection')
How to Fix CVE-2026-35656: Cwe-290: authentication bypass by spoofing in OpenClaw , Cwe-290: authentication bypass by spoofing in OpenClaw
How to Fix CVE-2026-7513: Buffer Overflow in HiPER 1200GW , Buffer Overflow in HiPER 1200GW
How to Fix CVE-2026-24410: Input Validation Flaw in iccDEV , Input Validation Flaw in iccDEV

*By Sai Kiran Pandrala*

⚡ At a glance


Severity	CVSS 7.1, High
Actively exploited?	No
Affected	hexpm (0 < 495f01607d3eae4aed7ad09b2f54f31ec7a7df01); Hexpm hex.pm (0 < 2026-03-10)
Fixed in	495f01607d3eae4aed7ad09b2f54f31ec7a7df01, 2026-03-10
Type (CWE)	CWE-400: CWE-400 Uncontrolled Resource Consumption

What is CVE-2026-23940?

Uncontrolled Resource Consumption vulnerability in hexpm hexpm/hexpm allows Excessive Allocation. Publishing an oversized package can cause Hex.pm to run out of memory while extracting the uploaded package tarball. This can terminate the affected application instance and result in a denial of service for package publishing and potentially other package-processing functionality.

In practical terms, a successful attacker gets a denial-of-service condition that crashes or hangs the affected service. There is no confirmed in-the-wild exploitation listed in CISA's KEV catalog at the time of writing, but the CVSS rating still warrants prompt patching.

Am I affected?

You're affected if you run hexpm at any version in the Affected row above. Use these probes to find your installed build:


# Confirm the installed version via your package manager
dpkg -l | grep -i hexpm   # Debian/Ubuntu
rpm -qa | grep -i hexpm   # RHEL/CentOS/Rocky

How to fix CVE-2026-23940

The primary fix is to upgrade to the patched build listed in the Fixed in row above (495f01607d3eae4aed7ad09b2f54f31ec7a7df01, 2026-03-10). Pick the platform that matches your install and run the commands below.

Linux (Ubuntu / Debian)


sudo apt-get update
sudo apt-get install --only-upgrade hexpm
# Confirm the installed version meets or exceeds 495f01607d3eae4aed7ad09b2f54f31ec7a7df01
dpkg -s hexpm | grep ^Version

Linux (RHEL / CentOS / Rocky)


sudo dnf upgrade --security hexpm -y
rpm -q hexpm

Windows (PowerShell, admin)


# Try winget first
winget upgrade --id 'Hexpm.hexpm' --silent --accept-source-agreements --accept-package-agreements
# If winget does not know the product, download the patched installer from the vendor and:
Start-Process -FilePath "$env:TEMP\hexpm-495f01607d3eae4aed7ad09b2f54f31ec7a7df01.msi" -ArgumentList '/qn /norestart' -Wait

PowerShell script (Windows) - detect, back up, upgrade, verify, log


# Run as Administrator
$ErrorActionPreference = 'Stop'
$log = "$env:ProgramData\hexpm-Patch-CVE-2026-23940.log"
function Write-Log($msg) { "$(Get-Date -Format s)  $msg" | Tee-Object -FilePath $log -Append }

Write-Log "Starting CVE-2026-23940 remediation for Hexpm hexpm"

# 1. Detect: replace the path/version probe with one valid for your install
$installed = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*hexpm*' } |
    Select-Object -First 1 -ExpandProperty Version)
Write-Log "Detected version: $installed"

if (-not $installed) {
    Write-Log "Product not installed on this host; nothing to do."
    return
}
if ([version]$installed -ge [version]'495f01607d3eae4aed7ad09b2f54f31ec7a7df01') {
    Write-Log "Already at fixed version $installed; no action needed."
    return
}

# 2. Backup configuration to a timestamped folder
$backup = "$env:ProgramData\hexpm-Backup-$(Get-Date -Format yyyyMMdd-HHmm)"
New-Item -ItemType Directory -Path $backup -Force | Out-Null
# Adjust the source path to match your install
$src = "$env:ProgramFiles\Hexpm\hexpm"
if (Test-Path $src) { Copy-Item -Path $src -Destination $backup -Recurse -Force }
Write-Log "Backed up config to $backup"

# 3. Apply the patched installer (place the verified file on a share or staging path)
$installer = "$env:TEMP\hexpm-495f01607d3eae4aed7ad09b2f54f31ec7a7df01.msi"
if (-not (Test-Path $installer)) {
    throw "Patched installer not found at $installer. Stage it from your software repo first."
}
Start-Process msiexec.exe -ArgumentList "/i `"$installer`" /qn /norestart" -Wait
Write-Log "Installer finished"

# 4. Verify
$verify = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*hexpm*' } |
    Select-Object -First 1 -ExpandProperty Version)
if ([version]$verify -ge [version]'495f01607d3eae4aed7ad09b2f54f31ec7a7df01') {
    Write-Log "SUCCESS: now at $verify (>= 495f01607d3eae4aed7ad09b2f54f31ec7a7df01)"
} else {
    Write-Log "FAILURE: still at $verify after install"
    exit 1
}

Bash script (Linux) - detect, back up, upgrade, verify, log


#!/usr/bin/env bash
set -euo pipefail
LOG=/var/log/hexpm-patch-cve-2026-23940.log
log()  { echo "$(date -Iseconds)  $*" | tee -a "$LOG"; }

log "Starting CVE-2026-23940 remediation for Hexpm hexpm"

# 1. Detect installed version (works for deb and rpm packages)
if command -v dpkg >/dev/null && dpkg -s hexpm >/dev/null 2>&1; then
    CURRENT=$(dpkg-query -W -f='${Version}' hexpm)
    PKG_MGR=apt
elif command -v rpm >/dev/null && rpm -q hexpm >/dev/null 2>&1; then
    CURRENT=$(rpm -q --queryformat '%{VERSION}' hexpm)
    PKG_MGR=dnf
else
    log "hexpm not installed via apt or rpm; check your package manager or vendor instructions."
    exit 0
fi
log "Detected: hexpm=$CURRENT (manager=$PKG_MGR)"

# 2. Backup config
BACKUP=/var/backups/hexpm-$(date +%Y%m%d-%H%M)
mkdir -p "$BACKUP"
for d in /etc/hexpm /etc/${pkg%%-*} ; do
    [ -d "$d" ] && cp -a "$d" "$BACKUP/" && log "Backed up $d to $BACKUP"
done

# 3. Upgrade
if [ "$PKG_MGR" = apt ]; then
    sudo apt-get update -y
    sudo apt-get install --only-upgrade -y hexpm
else
    sudo dnf upgrade --security -y hexpm
fi

# 4. Verify
if [ "$PKG_MGR" = apt ]; then
    NEW=$(dpkg-query -W -f='${Version}' hexpm)
else
    NEW=$(rpm -q --queryformat '%{VERSION}' hexpm)
fi
log "After upgrade: $NEW"

# Optionally compare against 495f01607d3eae4aed7ad09b2f54f31ec7a7df01 with dpkg --compare-versions or sort -V
log "Done. Restart the affected service if the package install did not."

If you can't patch immediately

These are runnable hardening commands. They reduce blast radius but they're not a replacement for the vendor patch.

Rate-limit and watchdog the affected service

Linux:


# Drop traffic above 50 connections/second from a single source
sudo iptables -A INPUT -p tcp --dport 443 -m conntrack --ctstate NEW -m limit --limit 50/s -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 443 -m conntrack --ctstate NEW -j DROP

Set systemd to auto-restart the service on crash:


[Service]
Restart=always
RestartSec=5s

How to verify the fix worked

Run the version probe again and confirm the running build matches the Fixed in row above.


# Confirm the running build matches the patched version listed by the vendor
# Example for Linux package installs:
dpkg -l | grep -i "hexpm"   # Debian/Ubuntu
rpm -qa | grep -i "hexpm"   # RHEL/CentOS/Rocky

Expected output: the package version should meet or exceed 495f01607d3eae4aed7ad09b2f54f31ec7a7df01.

Then re-run any vulnerability scanner you used previously and confirm the finding for CVE-2026-23940 has cleared. Sweep your logs for the indicators of compromise listed in the vendor or CISA advisory, especially if the system was internet-reachable during the disclosure window.

Frequently asked questions

Is CVE-2026-23940 being actively exploited?