CVE-2026-64607 is a medium-severity (CVSS 5.3) CWE-772 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 HttpComponents Client: Connection Leak on Content-Encoding Decode Error Leads to Pool Exhaustion DoS
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-2026-64607.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-64607 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
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
HttpClient based on the classic i/o model fails to correctly release the underlying connection back to the connection manager if it encounters an invalid or unsupported Content-Encoding header value in the response message. Please note this defect does not affect HttpClient based on the async i/o model.
This issue affects Apache HttpComponents Client: from 5.0-alpha1 through 5.6.2.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.httpcomponents.client5:httpclient5 | ≥ 5.0-alpha1&&< 5.6.3 | 5.6.3org.apache.httpcomponents.client5:httpclient5:5.6.3 |
Affected Products
httpclientapacheDetection & 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 5.6.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-64607 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.
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.
This is an Important flaw in Apache HttpComponents Client's classic I/O model, where an invalid `Content-Encoding` header in a response can prevent proper connection release. This connection leak can exhaust the connection pool, leading to a denial of service for applications utilizing the affected client. The…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.Source: Red Hat security advisory for CVE-2026-64607 (CC BY 4.0)
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Build of Apache Camel 3.33 for Quarkus 3.33.3.SP1 | httpclient5 | RHSA-2026:63302 |
| Red Hat build of Apache Camel 4.18.4 for Spring Boot 3.5.16 | httpclient5 | RHSA-2026:71675 |
| Red Hat build of Quarkus 3.27.5.SP1 | quarkus-apache-httpclient | RHSA-2026:62515 |
| 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 |
Frequently Asked Questions
Is CVE-2026-64607 in your dependencies?
Find it across Maven, including transitive dependencies.