Vulnerability identifier: #VU20340

Vulnerability risk: Medium

CVSSv3.1: 6.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2019-9517

CWE-ID: CWE-399

Exploitation vector: Network

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to incorrect implementation of HTTP/2 protocol. A remote attacker can  open 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.

Mitigation
Install updates from vendor's website.

External links
http://www.openwall.com/lists/oss-security/2019/08/15/7
http://github.com/Netflix/security-bulletins/blob/master/advisories/third-party/2019-002.md
http://kb.cert.org/vuls/id/605641/
http://lists.apache.org/thread.html/4610762456644181b267c846423b3a990bd4aaea1886ecc7d51febdb@%3Cannounce.httpd.apache.org%3E
http://lists.apache.org/thread.html/56c2e7cc9deb1c12a843d0dc251ea7fd3e7e80293cde02fcd65286ba@%3Ccvs.httpd.apache.org%3E
http://lists.apache.org/thread.html/d89f999e26dfb1d50f247ead1fe8538014eb412b2dbe5be4b1a9ef50@%3Cdev.httpd.apache.org%3E
http://lists.apache.org/thread.html/ec97fdfc1a859266e56fef084353a34e0a0b08901b3c1aa317a43c8c@%3Cdev.httpd.apache.org%3E
http://support.f5.com/csp/article/K02591030
http://www.synology.com/security/advisory/Synology_SA_19_33

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.