CVE-2026-40542 is a high-severity (CVSS 7.3) CWE-304 vulnerability in org.apache.httpcomponents.client5:httpclient5. A fix is available for org.apache.httpcomponents.client5:httpclient5 — see the affected versions and patch details below.
Apache HttpClient: SCRAM-SHA-256 mutual authentication bypass may cause the client to accept authentication without proper mutual authentication verification
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-40542.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-40542 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
org.apache.httpcomponents.client5:httpclient5Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
Missing critical step in authentication in Apache HttpClient 5.6 allows an attacker to cause the client to accept SCRAM-SHA-256 authentication without proper mutual authentication verification. Users are recommended to upgrade to version 5.6.1, which fixes this issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.httpcomponents.client5:httpclient5 | ≥ 5.6-alpha1&&< 5.6.1 | 5.6.1org.apache.httpcomponents.client5:httpclient5:5.6.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.httpcomponents.client5:httpclient5, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.apache.httpcomponents.client5:httpclient5 to 5.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-40542 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-40542 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-40542. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
| Product | Fixed in | Advisory |
|---|---|---|
| OpenShift Developer Tools and Services 4.12 | ocp-tools-4/jenkins-rhel8:1786628667 | RHSA-2026:60247 |
| OpenShift Developer Tools and Services 4.13 | ocp-tools-4/jenkins-rhel8:1786628681 | RHSA-2026:60249 |
| OpenShift Developer Tools and Services 4.14 | ocp-tools-4/jenkins-rhel8:1786533561 | RHSA-2026:60248 |
| OpenShift Developer Tools and Services 4.15 | ocp-tools-4/jenkins-rhel8:1786533565 | RHSA-2026:60239 |
| OpenShift Developer Tools and Services 4.16 | ocp-tools-4/jenkins-rhel9:1787125166 | RHSA-2026:60251 |
| OpenShift Developer Tools and Services 4.17 | ocp-tools-4/jenkins-rhel9:1787124635 | RHSA-2026:60246 |
| OpenShift Developer Tools and Services 4.18 | ocp-tools-4/jenkins-rhel9:1787125069 | RHSA-2026:60250 |
| OpenShift Developer Tools and Services 4.19 | ocp-tools-4/jenkins-rhel9:1787124632 | RHSA-2026:60252 |
Frequently Asked Questions
Is CVE-2026-40542 in your dependencies?
O3 Security finds CVE-2026-40542 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.