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Vulnerabilities

Security incident · CVE-2019-9516

Some HTTP/2 implementations are vulnerable to a header leak, 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-2019-9516 is not in CISA KEV. FIRST estimates a 57.46% 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
Medium6.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
57.46%
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 a header leak, potentially leading to a denial of service. The attacker sends a stream of headers with a 0-length header name and 0-length header value, optionally Huffman encoded into 1-byte or greater headers. Some implementations allocate memory for these headers and keep the allocation alive until the session dies. This can consume excess memory.

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-2019-9516

What to do

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

Should you patch?

CVE-2019-9516 is not in CISA KEV. FIRST estimates a 57.46% 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 57.46%. 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 a header leak, potentially leading to a denial of service. The attacker sends a stream of headers with a 0-length header name and 0-length header value, optionally Huffman encoded into 1-byte or greater headers. Some implementations allocate memory for these headers and keep the allocation alive until the session dies. This can consume excess memory.

  2. Jun 17, 2026 · Monitored products — high

    Updated

    Some HTTP/2 implementations are vulnerable to a header leak, potentially leading to a denial of service. The attacker sends a stream of headers with a 0-length header name and 0-length header value, optionally Huffman encoded into 1-byte or greater headers. Some implementations allocate memory for these headers and keep the allocation alive until the session dies. This can consume excess memory.

Sources

  • CVE.orgVulnerability recordCVE-2019-9516

    Official CVE identifier

    cve.org
  • Monitored products — highVendor advisoryCVE-2019-9516

    Some HTTP/2 implementations are vulnerable to a header leak, potentially leading to a denial of service. The attacker sends a stream of headers with a 0-length header name and 0-length header value, optionally Huffman encoded into 1-byte or greater headers. Some implementations allocate memory for these headers and keep the allocation alive until the session dies. This can consume excess memory.

    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