CVE-2019-9515
Some HTTP/2 implementations are vulnerable to a settings flood, potentially leading to a denial of service
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Description
Some HTTP/2 implementations are vulnerable to a settings flood, potentially leading to a denial of service. The attacker sends a stream of SETTINGS frames to the peer. Since the RFC requires that the peer reply with one acknowledgement per SETTINGS frame, an empty SETTINGS frame is almost equivalent in behavior to a ping. Depending on how efficiently this data is queued, this can consume excess CPU, memory, or both.
Official description from the CVE record, published by certcc. Copyright © 1999-2026 The MITRE Corporation. See /security/cve/legal for the CVE license. View the record on cve.org
Key data
CVSS 3.0 High 7.5
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector: Network
The vulnerable component can be reached over a network, possibly from the Internet.
Attack complexity: Low
No special conditions are needed. The attack can be repeated at will.
Privileges required: None
No account or privileges are needed.
User interaction: None
No action from any user is needed.
Scope: Unchanged
The impact stays within the vulnerable component.
Confidentiality impact: None
No effect on the secrecy of data.
Integrity impact: None
No effect on the trustworthiness of data.
Availability impact: High
Serious or total effect on availability.
| Metric | Value | What it means |
|---|---|---|
| Attack vector | Network | The vulnerable component can be reached over a network, possibly from the Internet. |
| Attack complexity | Low | No special conditions are needed. The attack can be repeated at will. |
| Privileges required | None | No account or privileges are needed. |
| User interaction | None | No action from any user is needed. |
| Scope | Unchanged | The impact stays within the vulnerable component. |
| Confidentiality impact | None | No effect on the secrecy of data. |
| Integrity impact | None | No effect on the trustworthiness of data. |
| Availability impact | High | Serious or total effect on availability. |
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EPSS
- Score
- 0.87286 (87.3% probability)
- Percentile
- 99.8%
- Scores of
- Nov 10, 2026
- Model
- v2026.06.15
Weakness (CWE)
- CWE-400Uncontrolled Resource Consumption
References
- VU#605641 (kb.cert.org)third-party-advisory
- github.com/Netflix/security-bulletins/blob/master/advisorie…
- [trafficserver-dev] 20190813 Apache Traffic Server is vulnerable to various HTTP/2 attacks (lists.apache.org)mailing-list
- [trafficserver-users] 20190813 Apache Traffic Server is vulnerable to various HTTP/2 attacks (lists.apache.org)mailing-list
- [trafficserver-announce] 20190813 Apache Traffic Server is vulnerable to various HTTP/2 attacks (lists.apache.org)mailing-list
- 20190814 APPLE-SA-2019-08-13-5 SwiftNIO HTTP/2 1.5.0 (seclists.org)mailing-list
- 20190816 APPLE-SA-2019-08-13-5 SwiftNIO HTTP/2 1.5.0 (seclists.org)mailing-list
- synology.com/security/advisory/Synology_SA_19_33
- support.f5.com/csp/article/K50233772
- security.netapp.com/advisory/ntap-20190823-0005
- FEDORA-2019-5a6a7bc12c (lists.fedoraproject.org)vendor-advisory
- FEDORA-2019-6a2980de56 (lists.fedoraproject.org)vendor-advisory
- 20190825 [SECURITY] [DSA 4508-1] h2o security update (seclists.org)mailing-list
- DSA-4508 (debian.org)vendor-advisory
- DSA-4520 (debian.org)vendor-advisory
- 20190910 [SECURITY] [DSA 4520-1] trafficserver security update (seclists.org)mailing-list
- openSUSE-SU-2019:2114 (lists.opensuse.org)vendor-advisory
- openSUSE-SU-2019:2115 (lists.opensuse.org)vendor-advisory
- kc.mcafee.com/corporate/index?page=content&id=SB10296
- RHSA-2019:2766 (access.redhat.com)vendor-advisory
- RHSA-2019:2796 (access.redhat.com)vendor-advisory
- RHSA-2019:2861 (access.redhat.com)vendor-advisory
- RHSA-2019:2925 (access.redhat.com)vendor-advisory
- RHSA-2019:2939 (access.redhat.com)vendor-advisory
- RHSA-2019:2955 (access.redhat.com)vendor-advisory
- support.f5.com/csp/article/K50233772?utm_source=f5support&a…
- RHSA-2019:3892 (access.redhat.com)vendor-advisory
- RHSA-2019:4018 (access.redhat.com)vendor-advisory
- RHSA-2019:4019 (access.redhat.com)vendor-advisory
- RHSA-2019:4021 (access.redhat.com)vendor-advisory
- RHSA-2019:4020 (access.redhat.com)vendor-advisory
- RHSA-2019:4045 (access.redhat.com)vendor-advisory
- RHSA-2019:4042 (access.redhat.com)vendor-advisory
- RHSA-2019:4040 (access.redhat.com)vendor-advisory
- RHSA-2019:4041 (access.redhat.com)vendor-advisory
- RHSA-2019:4352 (access.redhat.com)vendor-advisory
- RHSA-2020:0727 (access.redhat.com)vendor-advisory
- USN-4308-1 (usn.ubuntu.com)vendor-advisory
Timeline
- ID reserved
- Record published
- Record last updated
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Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 19:49 UTC. Sources and licenses