CVE-2024-45397

H2O alllows bypassing address-based access control with 0-RTT

HIGH
7.5
CVSS Score
Published: October 11, 2024 at 02:24 PM UTC
Updated: June 17, 2026 at 07:54 AM UTC
2 products affected across 2 vendorsH2OH2O

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Severity
HIGH7.5
Exploit prediction
EPSS 0.4%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 2024-10-10
Affected range stops below 2024-10-10, so it looks safe — our inference, not a vendor statement
v < 15ed15a2efb83a77bb4baaa5a119e639c2f6898a

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
NONE
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-284CWE-290

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