● Medium · CVSS 6.5

How to Fix CVE-2026-2734: Access Control Bypass in mlflow/mlflow

Q: Is CVE-2026-2734 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-2026-2734?

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: How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for mlflow/mlflow run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

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

How to Fix CVE-2026-41571: Improper Authentication in note-mark — Improper Authentication in note-mark
How to Fix CVE-2026-33949: @tinacms/graphql has Path Traversal that leads to overwrite of arbitrary files — @tinacms/graphql has Path Traversal that leads to overwrite of arbitrary files
How to Fix CVE-2026-7036: Path Traversal in i9 , Path Traversal in i9
How to Fix CVE-2026-1153: Critical Vulnerability in mpay , Critical Vulnerability in mpay
How to Fix CVE-2026-40493: Out-of-bounds write in sail , Out-of-bounds write in sail

*By Sai Kiran Pandrala*

⚡ At a glance


Severity	CVSS 6.5 - Medium
Actively exploited?	Not currently listed in CISA KEV
Affected	unspecified < 3.10.0
Fixed in	See vendor advisory
Type (CWE)	CWE-284: Improper Access Control

What is CVE-2026-2734?

CVE-2026-2734 is an access control bypass flaw in mlflow/mlflow. Authenticated or in some cases unauthenticated requests reach endpoints they should not be allowed to call, exposing administrative functionality or sensitive data. Vendor description: In mlflow/mlflow versions up to 3.9.0, the SearchModelVersions REST API endpoint and the mlflowSearchModelVersions GraphQL query lack proper per-model authorization checks when basic authentication is enabled. This allows any authenticated user to enumerate all model versions across all registered models, regardless of their permission level.

Why this CVE matters

Access control flaws let an attacker reach endpoints the developers assumed would be reserved for administrators. The impact depends on what those endpoints expose, but for management products the answer is usually configuration changes, log access, or credential reads.

For deployments of mlflow/mlflow 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:

mlflow/mlflow: unspecified < 3.10.0

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 mlflow/mlflow'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-2026-2734

Read the vendor advisory in full: https://huntr.com/bounties/d632f783-b2c7-4a3b-af5e-1d693e841c08
Upgrade mlflow/mlflow to the patched build listed in the vendor advisory.
Back up the configuration (and database, where applicable) before upgrading.
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.

npm / Yarn / pnpm


# Vendor advisory: https://huntr.com/bounties/d632f783-b2c7-4a3b-af5e-1d693e841c08
# Update to the patched release named in the advisory
npm install mlflow-mlflow@latest
# or pin to the exact fixed version from the vendor advisory
npm install mlflow-mlflow@<patched-version>
npm ls mlflow-mlflow

PyPI (pip / Poetry)


# Vendor advisory: https://huntr.com/bounties/d632f783-b2c7-4a3b-af5e-1d693e841c08
pip install --upgrade mlflow-mlflow
pip show mlflow-mlflow | grep -i version
# Poetry:
poetry add mlflow-mlflow@^<patched-version>

Docker / container


# Vendor advisory: https://huntr.com/bounties/d632f783-b2c7-4a3b-af5e-1d693e841c08
docker pull <your-registry>/mlflow-mlflow:<patched-tag>
docker stop <app> && docker rm <app>
docker run -d --name <app> <your-registry>/mlflow-mlflow:<patched-tag>

PowerShell detect/upgrade/verify/log (Windows)


# CVE-2026-2734 remediation runner. Adapt version checks to your environment.
$log = "C:\Logs\CVE-2026-2734-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 'mlflow/mlflow' }
    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
    $backup = "C:\Backup\CVE-2026-2734-$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 'mlflow/mlflow' }
    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-2026-2734 remediation runner. Re-runnable, exits non-zero on failure.
set -euo pipefail
log() { printf '%s %s\n' "$(date -Is)" "$*" | tee -a /var/log/cve-2026-2734-fix.log; }

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

log "Backup: snapshotting config"
backup="/var/backups/cve-2026-2734-$(date +%Y%m%d-%H%M)"
mkdir -p "$backup"
[ -d /etc/mlflowmlflow ] && cp -a /etc/mlflowmlflow "$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 mlflowmlflow
elif command -v dnf >/dev/null 2>&1; then
    sudo dnf upgrade -y mlflowmlflow
elif command -v yum >/dev/null 2>&1; then
    sudo yum update -y mlflowmlflow
fi

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

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

If you cannot patch immediately

No official workaround exists beyond restricting network exposure to the affected component. Apply the vendor patch as the primary remediation.

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-2026-2734.
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 log entries that do not match your normal request patterns, especially repeated requests to the same uncommon endpoint, and any administrative changes you cannot tie back to a known operator.

Frequently asked questions

Is CVE-2026-2734 being exploited in the wild?