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Vulnerabilities

Vulnerability · CVE-2019-9511

Some HTTP/2 implementations are vulnerable to window size manipulation and stream prioritization manipulation, potentially leading to a denial of service.

Published Aug 13, 2019 · catalog updated Jun 17, 2026 · Some HTTP/2 implementations are

Last checked Nov 9, 2026. A connected source was read within the last 7 days.

Check this week

CVE-2019-9511 is not in CISA KEV. FIRST estimates a 59.55% chance of exploitation in the next 30 days. Check whether you run Some HTTP/2 implementations are.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (Some HTTP/2 implementations are).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
59.55%
Remediation
Version ranges on file
Affected products
cpe apache/traffic server · cpe apple/swiftnio · cpe canonical/ubuntu linux

Some HTTP/2 implementations are vulnerable to window size manipulation and stream prioritization manipulation, potentially leading to a denial of service. The attacker requests a large amount of data from a specified resource over multiple streams. They manipulate window size and stream priority to force the server to queue the data in 1-byte chunks. Depending on how efficiently this data is queued, this can consume excess CPU, memory, or both.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe apache/traffic server>= 6.0.0, <= 6.2.3
  • cpe apache/traffic server>= 7.0.0, <= 7.1.6
  • cpe apache/traffic server>= 8.0.0, <= 8.0.3
  • cpe apple/swiftnio>= 1.0.0, <= 1.4.0
  • cpe canonical/ubuntu linux16.04
  • cpe canonical/ubuntu linux18.04

How to fix CVE-2019-9511

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2019-9511 is not in CISA KEV. FIRST estimates a 59.55% chance of exploitation in the next 30 days. Check whether you run Some HTTP/2 implementations are.

Which versions are affected?

Compare what you have installed with apache/traffic server >= 6.0.0, <= 6.2.3; apache/traffic server >= 7.0.0, <= 7.1.6; apache/traffic server >= 8.0.0, <= 8.0.3; canonical/ubuntu linux 16.04. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-400: Uncontrolled Resource Consumption; CWE-770: Allocation of Resources Without Limits or Throttling. EPSS 59.55%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Aug 13, 2019 · Monitored products — high

    Detected

    Some HTTP/2 implementations are vulnerable to window size manipulation and stream prioritization manipulation, potentially leading to a denial of service. The attacker requests a large amount of data from a specified resource over multiple streams. They manipulate window size and stream priority to force the server to queue the data in 1-byte chunks. Depending on how efficiently this data is queue

  2. Jun 17, 2026 · Monitored products — high

    Updated

    Some HTTP/2 implementations are vulnerable to window size manipulation and stream prioritization manipulation, potentially leading to a denial of service. The attacker requests a large amount of data from a specified resource over multiple streams. They manipulate window size and stream priority to force the server to queue the data in 1-byte chunks. Depending on how efficiently this data is queue

Sources

  • CVE.orgVulnerability recordCVE-2019-9511

    Official CVE identifier

    cve.org
  • Monitored products — highVendor advisoryCVE-2019-9511

    Some HTTP/2 implementations are vulnerable to window size manipulation and stream prioritization manipulation, potentially leading to a denial of service. The attacker requests a large amount of data from a specified resource over multiple streams. They manipulate window size and stream priority to force the server to queue the data in 1-byte chunks. Depending on how efficiently this data is queue

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 9, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgNov 6, 2026
  • Monitored products — highNov 6, 2026