CVE-2026-64607: Apache HttpComponents Client resource leak in classic I/O model

CVE-2026-64607 · Severity: medium · CVSS 5.3 · Published 2026-07-31

Apache HttpComponents Client is an HTTP client library used by applications to communicate with web services. When the library encounters an invalid or unsupported Content-Encoding header in an HTTP response, it fails to properly release the network connection back to its connection pool. An attacker can exploit this by sending specially crafted responses to exhaust the connection pool, causing the application to run out of available connections and resulting in a denial of service.

Technologies: org.apache.httpcomponents.client5:httpclient5 (Maven). Vendors: Apache Software Foundation, Maven.

Quick answers

Is CVE-2026-64607 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-64607 being exploited in the wild.
How severe is CVE-2026-64607?
Medium severity, with a CVSS score of 5.3, published 31 July 2026.
Which products and versions are affected?
Apache Software Foundation HttpComponents Client 5.0-alpha1 through 5.6.2; org.apache.httpcomponents.client5:httpclient5 (Maven) >= 5.0-alpha1, < 5.6.3, ECOSYSTEM:introduced=5.0-alpha1,fixed=5.6.3.
Is there a fix for CVE-2026-64607?
Yes. org.apache.httpcomponents.client5:httpclient5 (Maven): upgrade to 5.6.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-64607 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-64607?
Check whether you run Apache Software Foundation HttpComponents Client or org.apache.httpcomponents.client5:httpclient5 (Maven) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • org.apache.httpcomponents.client5:httpclient5 (Maven): upgrade to 5.6.3 or later
    # set org.apache.httpcomponents.client5:httpclient5 to 5.6.3 in your pom.xml or build.gradle

Technical details

The vulnerability is a resource leak in Apache HttpComponents Client's classic I/O model (the async I/O model is unaffected). The root cause is improper exception handling in the Content-Encoding decoding logic—when the library encounters an invalid or unsupported Content-Encoding header value in an HTTP response, the connection is not returned to the connection manager's pool for reuse. An attacker on the network can trigger this leak by sending responses with malformed Content-Encoding headers, causing connections to accumulate and eventually exhaust the pool. This leads to denial of service as legitimate requests are unable to obtain connections. The fix is available in version 5.6.3 and later.

Affected products

  • Apache HttpComponents Client 5.0-alpha1 through 5.6.2

Identifiers

  • CVE-2026-64607
  • GHSA-hjcp-jmpx-g3qm

Timeline

  • 2026-07-31: disclosed: Vulnerability published to GitHub Advisory Database
  • 2026-07-31: patched: Fix released in version 5.6.3

References

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