CVE-2019-9516 | Some HTTP/2 implementations are vulnerable to a header leak, potentially leading to a denial of service

Some HTTP/2 implementations are vulnerable to a header leak, potentially leading to a denial of service. The attacker sends a stream of headers with a 0-length header name and 0-length header value, optionally Huffman encoded into 1-byte or greater headers. Some implementations allocate memory for these headers and keep the allocation alive until the session dies. This can consume excess memory.

Published: 2019-08-13 Last update: 2025-01-14 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2019-9516 is rated Moderate Risk (55.5/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 2.13%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2019-9516

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-29 2.17% 2.13% -0.04%
2 2026-03-25 2.39% 2.17% -0.22%
3 2026-03-04 — 2.39% —

Full EPSS history (52 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2019-9516

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
7.5 3.0 HIGH
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]
6.8 2.0 MEDIUM
AV:N/AC:L/Au:S/C:N/I:N/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:C)
Complete availability impact.
 8.0 6.9 [email protected]

Weakness enumeration for CVE-2019-9516

OS Trackers for CVE-2019-9516

vendor priority summary link
alpine — CVE-2019-9516: 2 source package rows (nginx, nodejs); 20 state rows across 10 repos (3.10-main, 3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 20, open 0. https://security.alpinelinux.org/vuln/CVE-2019-9516
debian not yet assigned CVE-2019-9516 not yet assigned priority: Debian including 1 source packages (nginx), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2019-9516
redhat high — https://access.redhat.com/security/cve/CVE-2019-9516
suse low CVE-2019-9516 severity low: SUSE including 126 source package names (MozillaFirefox-68.2.0-78.51.4, MozillaFirefox-branding-SLED-68-21.9.8, …), 258 product×package rows across 23 product lines (SUSE Liberty Linux 8, SUSE Linux Enterprise Module for Open Buildservice Development Tools 15 SP3, … (23 product lines)): Fixed 242, Known Not Affected 16. https://www.suse.com/security/cve/CVE-2019-9516/
ubuntu medium CVE-2019-9516 medium priority: Ubuntu including 1 source packages (nginx), 6 status rows across 6 suites (bionic, cosmic, disco, trusty, upstream, xenial): released 3, ignored 1, needs-triage 1, not-affected 1. https://ubuntu.com/security/CVE-2019-9516

Affected software / configurations for CVE-2019-9516

Vendor Product Version Raw CPE
apple swiftnio >= 1.0.0, <= 1.4.0 cpe:2.3:a:apple:swiftnio:*:*:*:*:*:*:*:*
apache traffic_server >= 6.0.0, <= 6.2.3 cpe:2.3:a:apache:traffic_server:*:*:*:*:*:*:*:*
apache traffic_server >= 7.0.0, <= 7.1.6 cpe:2.3:a:apache:traffic_server:*:*:*:*:*:*:*:*
apache traffic_server >= 8.0.0, <= 8.0.3 cpe:2.3:a:apache:traffic_server:*:*:*:*:*:*:*:*
canonical ubuntu_linux 16.04 cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 18.04 cpe:2.3:o:canonical:ubuntu_linux:18.04:*:*:*:lts:*:*:*
canonical ubuntu_linux 19.04 cpe:2.3:o:canonical:ubuntu_linux:19.04:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
fedoraproject fedora 30 cpe:2.3:o:fedoraproject:fedora:30:*:*:*:*:*:*:*
synology skynas — cpe:2.3:a:synology:skynas:-:*:*:*:*:*:*:*
synology diskstation_manager 6.2 cpe:2.3:o:synology:diskstation_manager:6.2:*:*:*:*:*:*:*
synology vs960hd_firmware — cpe:2.3:o:synology:vs960hd_firmware:-:*:*:*:*:*:*:*
fedoraproject fedora 29 cpe:2.3:o:fedoraproject:fedora:29:*:*:*:*:*:*:*
fedoraproject fedora 32 cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*
opensuse leap 15.0 cpe:2.3:o:opensuse:leap:15.0:*:*:*:*:*:*:*
opensuse leap 15.1 cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*
redhat jboss_core_services 1.0 cpe:2.3:a:redhat:jboss_core_services:1.0:*:*:*:*:*:*:*
redhat jboss_enterprise_application_platform 7.2.0 cpe:2.3:a:redhat:jboss_enterprise_application_platform:7.2.0:*:*:*:*:*:*:*
redhat jboss_enterprise_application_platform 7.3.0 cpe:2.3:a:redhat:jboss_enterprise_application_platform:7.3.0:*:*:*:*:*:*:*
redhat openshift_service_mesh 1.0 cpe:2.3:a:redhat:openshift_service_mesh:1.0:*:*:*:*:*:*:*
redhat quay 3.0.0 cpe:2.3:a:redhat:quay:3.0.0:*:*:*:*:*:*:*
redhat software_collections 1.0 cpe:2.3:a:redhat:software_collections:1.0:*:*:*:*:*:*:*
redhat enterprise_linux 8.0 cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:*
oracle graalvm 19.2.0 cpe:2.3:a:oracle:graalvm:19.2.0:*:*:*:enterprise:*:*:*
mcafee web_gateway >= 7.7.2.0, < 7.7.2.24 cpe:2.3:a:mcafee:web_gateway:*:*:*:*:*:*:*:*
mcafee web_gateway >= 7.8.2.0, < 7.8.2.13 cpe:2.3:a:mcafee:web_gateway:*:*:*:*:*:*:*:*
mcafee web_gateway >= 8.1.0, < 8.2.0 cpe:2.3:a:mcafee:web_gateway:*:*:*:*:*:*:*:*
f5 nginx >= 1.9.5, < 1.16.1 cpe:2.3:a:f5:nginx:*:*:*:*:*:*:*:*
f5 nginx >= 1.17.0, <= 1.17.2 cpe:2.3:a:f5:nginx:*:*:*:*:*:*:*:*
nodejs node.js >= 8.0.0, < 8.16.1 cpe:2.3:a:nodejs:node.js:*:*:*:*:lts:*:*:*
nodejs node.js >= 10.0.0, < 10.16.3 cpe:2.3:a:nodejs:node.js:*:*:*:*:lts:*:*:*
nodejs node.js >= 12.0.0, < 12.8.1 cpe:2.3:a:nodejs:node.js:*:*:*:*:-:*:*:*

References for CVE-2019-9516

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00031.html Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00032.html Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00035.html Mailing List Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00014.html Mailing List Third Party Advisory
http://seclists.org/fulldisclosure/2019/Aug/16 Mailing List Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2745 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2746 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2775 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2799 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2925 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2939 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2946 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2950 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2955 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:2966 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:3932 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:3933 Third Party Advisory
https://access.redhat.com/errata/RHSA-2019:3935 Third Party Advisory
https://github.com/Netflix/security-bulletins/blob/master/advisories/third-party/2019-002.md Third Party Advisory
https://kb.cert.org/vuls/id/605641/ Third Party Advisory US Government Resource
https://kc.mcafee.com/corporate/index?page=content&id=SB10296 Third Party Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/4ZQGHE3WTYLYAYJEIDJVF2FIGQTAYPMC/
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/CMNFX5MNYRWWIMO4BTKYQCGUDMHO3AXP/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/H472D5HPXN6RRXCNFML3BK5OYC52CXF2/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/POPAEC4FWL4UU4LDEGPY5NPALU24FFQD/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TAZZEVTCN2B4WT6AIBJ7XGYJMBTORJU5/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/XHTKU7YQ5EEP2XNSAV4M4VJ7QCBOJMOD/
https://seclists.org/bugtraq/2019/Aug/24 Mailing List Third Party Advisory
https://seclists.org/bugtraq/2019/Aug/40 Mailing List Third Party Advisory
https://security.netapp.com/advisory/ntap-20190823-0002/ Third Party Advisory
https://security.netapp.com/advisory/ntap-20190823-0005/ Third Party Advisory
https://support.f5.com/csp/article/K02591030 Third Party Advisory
https://support.f5.com/csp/article/K02591030?utm_source=f5support&amp%3Butm_medium=RSS
https://usn.ubuntu.com/4099-1/ Third Party Advisory
https://www.debian.org/security/2019/dsa-4505 Third Party Advisory
https://www.synology.com/security/advisory/Synology_SA_19_33 Third Party Advisory
cvelogic Threat Intelligence