CameraRisk

CVE-2019-9511

Synology

Published
13 August 2019
Last modified
17 June 2026
CVSS
7.5 v3.1
Severity
high
EPSS
59.5% (99th pct)
CISA KEV
Not listed
NVD status
Modified
Weaknesses
CWE-400, CWE-770

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Description

Some HTTP/2 implementations are vulnerable to window size manipulation and stream prioritization manipulation, potentially leading to a denial of service. The attacker requests a large amount of data from a specified resource over multiple streams. They manipulate window size and stream priority to force the server to queue the data in 1-byte chunks. Depending on how efficiently this data is queued, this can consume excess CPU, memory, or both.

Exploitation

Not listed in the CISA Known Exploited Vulnerabilities catalogue as of 2026.09.04. That is an absence of confirmed public exploitation, not evidence that exploitation has not occurred. EPSS models a 59.5% probability of exploitation activity in the next 30 days, placing it in the top decile of all scored CVEs.

Affected products

ProductVendorTypeVersions named
VS960HD Synology unknown < 2.2.3-1505, < 2.3.6-1720

References

Vendor advisory and patch

CVE-2019-9511 at NVD

Record assembled from NVD, CISA KEV 2026.09.04 and FIRST EPSS 2026-09-04. Affected products are those NVD's CPE configuration names that fall inside this site's scope; a CVE may affect products outside it.