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CVE-2019-17638

Critical Vulnerability: CVE-2019-17638 — eclipse — jetty

In Eclipse Jetty, versions 9.4.27.v20200227 to 9.4.29.v20200521, in case of too large response headers, Jetty throws an exception to produce an HTTP 431 error. When this happens, the ByteBuffer containing the HTTP response headers is released back to the ByteBufferPool twice. Because of this double release, two threads can acquire the same ByteBuffer from the pool and while thread1 is about to use the ByteBuffer to write response1 data, thread2 fills the ByteBuffer with other data. Thread1 then

Sunday, August 9, 2026eclipseVulnios Threat Intelligence
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Vulnerability Snapshot

CVE-2019-17638 is rated CRITICAL — exploitation is trivial or already observed in the wild and impact is severe. Patch immediately, not on the next maintenance window.

Affected technology: jetty.

Executive Summary

In Eclipse Jetty, versions 9.4.27.v20200227 to 9.4.29.v20200521, in case of too large response headers, Jetty throws an exception to produce an HTTP 431 error. When this happens, the ByteBuffer containing the HTTP response headers is released back to the ByteBufferPool twice. Because of this double release, two threads can acquire the same ByteBuffer from the pool and while thread1 is about to use the ByteBuffer to write response1 data, thread2 fills the ByteBuffer with other data. Thread1 then proceeds to write the buffer that now contains different data. This results in client1, which issued request1 seeing data from another request or response which could contain sensitive data belonging to client2 (HTTP session ids, authentication credentials, etc.). If the Jetty version cannot be upgraded, the vulnerability can be significantly reduced by configuring a responseHeaderSize significantly larger than the requestHeaderSize (12KB responseHeaderSize and 8KB requestHeaderSize).

Why It Matters

CVE-2019-17638 is rated CRITICAL severity, requiring immediate attention from security teams.

CVSS Base Score: 9.4/10

Affected Technologies

Vendors: eclipse

Products: jetty

🛡️What Defenders Should Check

  • Check if you are affected — Review your asset inventory for products listed in CVE-2019-17638.
  • Apply available patches — Visit vendor advisories for the latest security updates.
  • Monitor for exploitation — Check your SIEM/IDS logs for related indicators.

    • Use Vulnios to continuously monitor your exposure to CVE-2019-17638 and similar vulnerabilities.

    References & Sources

  • http://www.openwall.com/lists/oss-security/2020/08/17/1
  • https://bugs.eclipse.org/bugs/show_bug.cgi?id=564984
  • https://lists.apache.org/thread.html/r29073905dc9139d0d7a146595694bf57bb9e35e5ec6aa73eb9c8443a%40%3Ccommits.pulsar.apache.org%3E
  • https://lists.apache.org/thread.html/r378e4cdec15e132575aa1dcb6296ffeff2a896745a8991522e266ad4%40%3Ccommits.pulsar.apache.org%3E
  • https://lists.apache.org/thread.html/r4bdd3f7bb6820a79f9416b6667d718a06d269018619a75ce4b759318%40%3Ccommits.pulsar.apache.org%3E
  • https://lists.apache.org/thread.html/r521168299e023fb075b57afe33d17ff1d09e8a10e0fd8c775ea0e028%40%3Ccommits.pulsar.apache.org%3E
  • https://lists.apache.org/thread.html/r7fc5f2ed49641ea91c433e3cd0fc3d31c0278c87b82b15c33b881415%40%3Ccommits.pulsar.apache.org%3E
  • https://lists.apache.org/thread.html/r81f58591fb4716fb867b36956f30c7c8ad4ab3f23abc952d9d86a2a0%40%3Ccommits.pulsar.apache.org%3E
  • https://lists.apache.org/thread.html/r9584c4304c888f651d214341a939bd264ed30c9e3d0d30fe85097ecf%40%3Ccommits.pulsar.apache.org%3E
  • https://lists.apache.org/thread.html/r9a2cfa56d30782a0c17a5deb951a622d1f5c8de48e1c3b578ffc2a84%40%3Ccommits.pulsar.apache.org%3E

    • How Vulnios Detects This

    Vulnios scans for this vulnerability using Trivy and Grype for SBOM-based CVE matching and Vulnios CVE feed continuous monitoring against your asset inventory. Run a scan against your environment to see whether you are exposed; findings are linked back to the original CVE record so triage starts with the patch path already known.

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    Affected Products

    jetty

    Sources

    Related Threat Alerts

    Frequently Asked Questions

    What is CVE-2019-17638?

    CVE-2019-17638 is a critical-severity vulnerability tracked under the Common Vulnerabilities and Exposures program. In Eclipse Jetty, versions 9.4.27.v20200227 to 9.4.29.v20200521, in case of too large response headers, Jetty throws an exception to produce an HTTP 431 error. When this happens, the ByteBuffer contai

    Am I affected?

    Check whether your environment runs jetty. If you operate any of those, treat yourself as in scope until you have evidence otherwise. A Vulnios scan will identify the exact assets carrying the affected version.

    How urgent is the response?

    Critical: do not wait for your normal patch cycle. Verify exposure today, apply the vendor patch immediately, and add detection rules for any post-exploit indicators.

    How do I remediate?

    Apply the vendor patch listed in the upstream advisory linked under Sources. If the patch is not yet available, follow the vendor-supplied workaround (often a config flag or feature disable) and add detections for the published exploit pattern in your SIEM. Re-scan after the patch lands to confirm the finding clears.

    Where can I track exploitation activity?

    Watch CISA's Known Exploited Vulnerabilities catalog for CVE-2019-17638. Cross-reference with public exploit databases and your own SIEM/IDS for indicator-of-compromise patterns. Vulnios tracks KEV status automatically and surfaces it on the asset findings view.

    How does Vulnios help with this?

    Vulnios continuously cross-references your asset inventory against the live CVE feed (NVD, vendor advisories, CISA KEV, and curated OSINT). When a new CVE matches your environment, you get a prioritized finding with the severity, KEV status, exploit-prediction (EPSS), and a direct path to the vendor patch. You can start a free scan from the homepage.

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