CVE-2016-4817

lib/http2/connection.c in H2O before 1.7.3 and 2.x before 2.0.0-beta5 mishandles HTTP/2 disconnection, which allows remote attackers to cause a denial of service (use-after-free and application crash) or possibly execute arbitrary code via a crafted packet.

Published: 2016-06-19 Last update: 2026-05-06 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2016-4817 is rated Moderate Risk (62.5/100): CVSS High severity, with high exploitation likelihood (EPSS 7.96%, 92th percentile). EPSS ranks this CVE among the most likely to be exploited in the near term. High exploitation likelihood—assess exposure and prioritize 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-2016-4817

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 2025-08-25 7.52% 7.96% +0.45%
2 2025-03-30 18.96% 7.52% -11.45%
3 2025-03-29 — 18.96% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2016-4817

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
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]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P 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:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2016-4817

OS Trackers for CVE-2016-4817

vendor priority summary link
debian unimportant CVE-2016-4817 unimportant priority: Debian including 1 source packages (h2o), 2 status rows across 2 suites (bookworm, bullseye): resolved 2. https://security-tracker.debian.org/tracker/CVE-2016-4817

NVD evaluator notes for CVE-2016-4817

Comment: <a href="http://cwe.mitre.org/data/definitions/416.html">CWE-416: Use After Free</a>

Affected software / configurations for CVE-2016-4817

Vendor Product Version Raw CPE
dena h2o <= 1.7.2 cpe:2.3:a:dena:h2o:*:*:*:*:*:*:*:*
dena h2o <= 2.0.0 cpe:2.3:a:dena:h2o:*:beta4:*:*:*:*:*:*

References for CVE-2016-4817

cvelogic Threat Intelligence