CVE-2024-45397 | H2O alllows bypassing address-based access control with 0-RTT

h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. When an HTTP request using TLS/1.3 early data on top of TCP Fast Open or QUIC 0-RTT packets is received and the IP-address-based access control is used, the access control does not detect and prohibit HTTP requests conveyed by packets with a spoofed source address. This behavior allows attackers on the network to execute HTTP requests from addresses that are otherwise rejected by the address-based access control. The vulnerability has been addressed in commit 15ed15a. Users may disable the use of TCP FastOpen and QUIC to mitigate the issue.

Published: 2024-10-11 Last update: 2024-11-12 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2024-45397 is rated Low Risk (35.7/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.44%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

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-2024-45397

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 2026-06-15 0.50% 0.44% -0.07%
2 2026-05-07 0.66% 0.50% -0.15%
3 2026-03-02 — 0.66% —

Full EPSS history (9 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2024-45397

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.9 3.1 MEDIUM
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N 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:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 3.6 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N 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:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2024-45397

OS Trackers for CVE-2024-45397

vendor priority summary link
alpine medium CVE-2024-45397: 1 source package rows (h2o); 2 state rows across 1 repos (edge-community); fixed 0, open 2. https://security.alpinelinux.org/vuln/CVE-2024-45397
debian not yet assigned CVE-2024-45397 not yet assigned priority: Debian including 1 source packages (h2o), 2 status rows across 2 suites (bookworm, bullseye): open 2. https://security-tracker.debian.org/tracker/CVE-2024-45397
ubuntu medium CVE-2024-45397 medium priority: Ubuntu including 1 source packages (h2o), 8 status rows across 8 suites (bionic, focal, jammy, noble, oracular, plucky, questing, upstream): needs-triage 5, ignored 2, DNE 1. https://ubuntu.com/security/CVE-2024-45397

Affected software / configurations for CVE-2024-45397

Vendor Product Version Raw CPE
dena h2o < 2024-10-10 cpe:2.3:a:dena:h2o:*:*:*:*:*:*:*:*

References for CVE-2024-45397

cvelogic Threat Intelligence