⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Medium · CVSS 4.8

How to Fix CVE-2026-40557: CWE-295 Improper Certificate Validation in Apache Storm Prometheus Reporter

By Sai Kiran Pandrala

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

Last verified: 2026-05-25

CVE-2026-40557 is a cwe-295 improper certificate validation in Apache Software Foundation Apache Storm Prometheus Reporter. Fix it by upgrading to the patched build from the vendor advisory.

⚡ At a glance
SeverityCVSS 4.8 - Medium
Actively exploited?Not currently in the CISA KEV catalog
AffectedApache Storm Prometheus Reporter 2.6.3 up to (excluding) 2.8.7
Fixed inSee vendor advisory
Type (CWE)CWE-295: CWE-295 Improper Certificate Validation

What is CVE-2026-40557?

CVE-2026-40557 is a cwe-295 improper certificate validation flaw in Apache Software Foundation Apache Storm Prometheus Reporter. It carries a CVSS base score of 4.8 (medium). It is not currently listed in the CISA Known Exploited Vulnerabilities catalog.

From the source record: Improper Certificate Validation via Global SSL Context Downgrade in Apache Storm Prometheus Reporter

Versions Affected: from 2.6.3 to 2.8.6

Description: 

In production deployments where an administrator enables storm.daemon.metrics.reporter.plugin.prometheus.skip_tls_validation (by default it is disabled) intending to affect only the Prometheus reporter, the undocumented global side effect creates an attack surface across every TLS-protected communication channel in the Storm daemon.

The PrometheusPreparableReporter class implements an INSECURE_TRUST_MANAGER that accepts all SSL certificates without validation, with empty checkClientTrusted and checkServerTrusted methods. Most critically, when the storm.daemon.metrics.reporter.plugin.prometheus.

Why it matters in practice: The blast radius depends on how the affected service is exposed. An internet-facing instance with no compensating controls is the highest-risk configuration.

Am I affected?

You are affected if your installation of Apache Storm Prometheus Reporter matches a version listed in the Affected row above.


# Debian/Ubuntu
dpkg -s apache | grep Version
# RHEL/Rocky
rpm -q apache

How to fix CVE-2026-40557

Apply the vendor patch. Target the build named in the Fixed in row above (See vendor advisory). The runnable command set below covers the most common deployment patterns for Apache Storm Prometheus Reporter.

Ubuntu / Debian


sudo apt-get update
sudo apt-get install --only-upgrade apache
dpkg -s apache | grep Version

RHEL / CentOS / Rocky


sudo dnf upgrade apache -y
rpm -q apache

After applying the patch

  1. Restart the service or device so the patched binary loads.
  2. Confirm the running version matches the Fixed in row using the verification command below.
  3. Rotate credentials and API keys that the affected service could access if the asset was exposed during the disclosure window.

If you can't patch immediately

Until the patch lands, narrow the attack surface with these runnable controls.

Restrict network exposure

Block public access to the affected service at the perimeter. Allow only trusted source IPs.


# Linux iptables: only allow trusted admin subnet
sudo iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 443 -j DROP
sudo iptables-save | sudo tee /etc/iptables/rules.v4


# Windows firewall: only allow trusted admin subnet on management port
New-NetFirewallRule -DisplayName "Restrict-Mgmt-Allow" -Direction Inbound -Action Allow `
  -RemoteAddress 10.10.10.0/24 -Protocol TCP -LocalPort 443
New-NetFirewallRule -DisplayName "Restrict-Mgmt-Deny"  -Direction Inbound -Action Block `
  -Protocol TCP -LocalPort 443

Mitigations are temporary. Apply the vendor patch as soon as a maintenance window opens.

How to verify the fix worked

Confirm the patched build is the one actually running.


# Debian/Ubuntu
dpkg -s apache | grep Version
# RHEL/Rocky
rpm -q apache

Expected: a version at or above the patched build named in the vendor advisory.

Also worth doing: pull recent log windows for indicators of compromise listed in the vendor advisory, and re-run an authenticated vulnerability scan with up-to-date signatures.

Frequently asked questions

Is CVE-2026-40557 being exploited in the wild?

As of 2026-05-25, CVE-2026-40557 is not listed in the CISA Known Exploited Vulnerabilities catalog. Watch the catalog and patch on a normal cadence; KEV status can change as exploitation evidence emerges.

What is the CVSS score for CVE-2026-40557?

The CVSS base score is 4.8 (Medium).

What version fixes this?

The vendor advisory names the patched build. See the References section.

Will a WAF or IDS rule alone close this?

No. Network filters cut down opportunistic scans but they do not remove the flaw. The vendor patch is the only durable fix.

References

*Assembled from the official vendor advisory, the NVD record, and the CISA KEV listing on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*