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CVE-2019-9515

Synology

Published
13 August 2019
Last modified
17 June 2026
CVSS
7.5 v3.1
Severity
high
EPSS
87.4% (100th 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 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.

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 87.4% 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

CVE-2019-9515 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.