● Critical · CVSS 9.3

How to Fix CVE-2026-26335: Deserialization RCE in VeraSMART

Q: Is CVE-2026-26335 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Q: Will a WAF or IDS rule fully mitigate CVE-2026-26335?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

Q: Do I need to assume compromise if my VeraSMART was internet-facing and unpatched?

For an unauthenticated RCE-class flaw exposed to the public internet during the known exploitation window, yes. Review logs, rotate credentials the process could access, and look for unexpected accounts, scheduled tasks, or outbound connections.

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

How to Fix CVE-2026-7061: OS Command Injection in chatgpt-mcp-server — OS Command Injection in chatgpt-mcp-server
How to Fix CVE-2026-25983: Use-after-free in ImageMagick — Use-after-free in ImageMagick
How to Fix CVE-2026-5210: Arbitrary File Read in Leave Application System , Arbitrary File Read in Leave Application System
How to Fix CVE-2026-4263: Access Control Bypass in HiJiffy Chatbot , Access Control Bypass in HiJiffy Chatbot
How to Fix CVE-2026-33941: Critical Vulnerability in handlebars.js , Critical Vulnerability in handlebars.js

*By Sai Kiran Pandrala*

⚡ At a glance


Severity	CVSS 9.3 - Critical
Actively exploited?	Not currently listed in CISA KEV
Affected	0 < 2022 R1
Fixed in	See vendor advisory
Type (CWE)	CWE-321: Use of Hard-coded Cryptographic Key

What is CVE-2026-26335?

CVE-2026-26335 is an unsafe deserialization in VeraSMART. The application accepts attacker-controlled serialized objects and reconstructs them without validating their type, so a crafted payload triggers code execution inside the running process. Unauthenticated remote code execution is the typical impact. Vendor description: Calero VeraSMART versions prior to 2022 R1 use static ASP.NET/IIS machineKey values configured for the VeraSMART web application and stored in C:\\Program Files (x86)\\Veramark\\VeraSMART\\WebRoot\\web.config. An attacker who obtains these keys can craft a valid ASP.NET ViewState payload that passes integrity validation and is accepted by the application, resulting in server-side deserialization and remote code execution in the context of the IIS application.

Why this CVE matters

Deserialization bugs are a favorite of ransomware operators because they convert a single HTTP request into full code execution on the target host. Public proof-of-concept code for this CVE class typically appears within days of disclosure, and weaponized exploits follow shortly after.

For deployments of VeraSMART that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

VeraSMART: 0 < 2022 R1

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Open VeraSMART's About dialog or run the vendor-documented version-check command. Compare the result against the affected ranges in the advisory.

How to fix CVE-2026-26335

Read the vendor advisory in full: https://www.calero.com/
Upgrade VeraSMART to the patched build listed in the vendor advisory.
Back up the configuration (and database, where applicable) before upgrading.
Rotate any credentials, API keys, or session tokens that the vulnerable service touched. An unauthenticated RCE-class flaw means anything the process could see should be treated as exposed.
Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
Restart the affected service so the patched binary loads, then verify the new version (see verification section).

The commands below are runnable starting points. Adapt the package name, target version, and host paths to your environment using the vendor advisory linked under References.

Ubuntu / Debian


sudo apt-get update
sudo apt-get install --only-upgrade verasmart
dpkg -s verasmart | grep -i version

RHEL / CentOS / Rocky / AlmaLinux


sudo dnf upgrade --refresh verasmart -y
rpm -q verasmart

Container image


# Vendor advisory: https://www.calero.com/
docker pull <your-registry>/verasmart:<patched-tag>
docker build -t <your-app>:patched .
docker stop <your-app> && docker rm <your-app>
docker run -d --name <your-app> <your-app>:patched

Windows (PowerShell, run as administrator)


# Vendor advisory: https://www.calero.com/
# Apply current Windows Updates - vendor patches ship as monthly rollups
Install-Module -Name PSWindowsUpdate -Force -SkipPublisherCheck -Confirm:$false
Import-Module PSWindowsUpdate
Get-WindowsUpdate -KBArticleID <KB-from-advisory>
Install-WindowsUpdate -KBArticleID <KB-from-advisory> -AcceptAll -AutoReboot

# Confirm the KB landed
Get-HotFix | Where-Object { $_.HotFixID -eq 'KB<id>' }

# Or, for an MSU file from the Microsoft Update Catalog:
wusa.exe C:\Patches\windows10.0-kb<id>-x64.msu /quiet /norestart
shutdown /r /t 60

PowerShell detect/upgrade/verify/log (Windows)


# CVE-2026-26335 remediation runner. Adapt version checks to your environment.
$log = "C:\Logs\CVE-2026-26335-fix.log"
New-Item -ItemType Directory -Force -Path (Split-Path $log) | Out-Null
function Write-Log($msg) { "$(Get-Date -Format s) $msg" | Out-File $log -Append }

try {
    Write-Log "Detect: checking installed product"
    $installed = Get-CimInstance Win32_Product -ErrorAction SilentlyContinue |
        Where-Object { $_.Name -match 'VeraSMART' }
    if (-not $installed) { Write-Log "Product not installed; nothing to do"; return }
    Write-Log "Found version $($installed.Version)"

    Write-Log "Backup: copying program files and registry hive"
    $stamp = Get-Date -Format yyyyMMdd-HHmm
    $backup = "C:\Backup\CVE-2026-26335-$stamp"
    New-Item -ItemType Directory -Force -Path $backup | Out-Null
    Copy-Item $installed.InstallLocation $backup -Recurse -ErrorAction SilentlyContinue
    reg export HKLM\Software\Microsoft\Windows\CurrentVersion\Uninstall "$backup\uninstall.reg" /y | Out-Null

    Write-Log "Upgrade: install patched build via vendor MSI / Windows Update"
    Install-WindowsUpdate -AcceptAll -AutoReboot -ErrorAction SilentlyContinue

    Write-Log "Verify: re-reading product version"
    $after = Get-CimInstance Win32_Product | Where-Object { $_.Name -match 'VeraSMART' }
    Write-Log "Post-patch version: $($after.Version)"
    if ($after.Version -ne $installed.Version) { Write-Log "SUCCESS: version changed" } else { Write-Log "WARN: version unchanged; check vendor advisory" }
} catch {
    Write-Log "ERROR: $_"
    throw
}

Bash detect/upgrade/verify/log (Linux)


#!/usr/bin/env bash
# CVE-2026-26335 remediation runner. Re-runnable, exits non-zero on failure.
set -euo pipefail
log() { printf '%s %s\n' "$(date -Is)" "$*" | tee -a /var/log/cve-2026-26335-fix.log; }

log "Detect: current verasmart version"
if command -v dpkg >/dev/null 2>&1; then
    current=$(dpkg-query -W -f='${Version}' verasmart 2>/dev/null || echo "not-installed")
elif command -v rpm >/dev/null 2>&1; then
    current=$(rpm -q --qf '%{VERSION}-%{RELEASE}' verasmart 2>/dev/null || echo "not-installed")
else
    current="unknown"
fi
log "Current: $current"

log "Backup: snapshotting config"
backup="/var/backups/cve-2026-26335-$(date +%Y%m%d-%H%M)"
mkdir -p "$backup"
[ -d /etc/verasmart ] && cp -a /etc/verasmart "$backup/" || true

log "Upgrade: applying vendor patch"
if command -v apt-get >/dev/null 2>&1; then
    sudo apt-get update -qq
    sudo apt-get install -y --only-upgrade verasmart
elif command -v dnf >/dev/null 2>&1; then
    sudo dnf upgrade -y verasmart
elif command -v yum >/dev/null 2>&1; then
    sudo yum update -y verasmart
fi

log "Verify: re-reading verasmart version"
if command -v dpkg >/dev/null 2>&1; then
    after=$(dpkg-query -W -f='${Version}' verasmart)
else
    after=$(rpm -q --qf '%{VERSION}-%{RELEASE}' verasmart)
fi
log "After: $after"

if [ "$after" != "$current" ]; then
    log "SUCCESS: verasmart upgraded"
else
    log "WARN: version unchanged. Confirm the patched build is in your repository."
    exit 1
fi

If you cannot patch immediately

There is no safe runtime mitigation for deserialization flaws beyond removing exposure: block the affected endpoint at a reverse proxy or WAF and restrict access to authenticated, trusted users only. Patch as soon as possible.

How to verify the fix worked

After applying the patch, verify the running version in the product's admin UI or via the vendor-documented CLI command.
Confirm the patched build matches the version listed in the vendor advisory.
Run an authenticated vulnerability scan with a current signature set and confirm the scanner no longer flags CVE-2026-26335.
Review logs for the entire pre-patch window for indicators of compromise listed in the vendor or CISA advisory.
Confirm any network-layer mitigations that were applied as a stopgap have been reverted (or left in place intentionally) once the patch is verified.

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for unexpected administrator accounts in VeraSMART, scheduled tasks or cron jobs you did not create, new files in web-accessible directories, and outbound connections to addresses not in your baseline. Suspicious requests to the vulnerable endpoint immediately followed by successful 200-class responses with unusually large bodies are a strong indicator of exploitation.

Frequently asked questions

Is CVE-2026-26335 being exploited in the wild?