CVE-2024-45397Network attack vector

Unauthorized request execution via spoofed 0-RTT addresses

Published Oct 11, 2024 · Updated Oct 11, 2024

Improper access control in h2o before 15ed15a allows remote attackers to execute blocked HTTP requests via spoofed 0-RTT traffic. The mruby ACL addr method evaluated REMOTE_ADDR or X-Forwarded-For for early-data requests instead of rejecting the request as too early. Exploitation requires IP-based ACLs plus TLS 1.3 early data over TCP Fast Open or QUIC 0-RTT; the result is access to HTTP resources barred to the spoofed address.

CVSS severity5.9
Medium
EPSS probability0.44%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper access control in h2o before 15ed15a allows remote attackers to execute blocked HTTP requests via spoofed 0-RTT traffic. The mruby ACL addr method evaluated REMOTE_ADDR or X-Forwarded-For for early-data requests instead of rejecting the request as too early. Exploitation requires IP-based ACLs plus TLS 1.3 early data over TCP Fast Open or QUIC 0-RTT; the result is access to HTTP resources barred to the spoofed address.

The record

CVE
CVE-2024-45397
Published
Oct 11, 2024
Updated
Oct 11, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-290, CWE-284, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Oct 11, 2024CVE publishedPublication date reported by the CVE source.
  2. Oct 11, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
5.9GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-290Authentication Bypass by Spoofing
CWE-284Improper Access Control
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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