CVE-2024-45403Network attack vector

Server crash via stale HTTP/3 stream linkage

Published Oct 11, 2024 · Updated Oct 11, 2024

Reachable assertion in H2O commits 16b13ee through 15ed15a allows remote attackers to crash reverse-proxy servers via HTTP/3 cancellation. The shutdown_stream function in lib/http3/server.c stops the QUIC receive side without unlinking the canceled stream from the pending-stream list, leaving stale state that reaches an assertion. Exploitation requires HTTP/3 and reverse-proxy mode; the standalone server normally restarts, but concurrent requests are interrupted.

CVSS severity3.7
Low
EPSS probability0.65%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Reachable assertion in H2O commits 16b13ee through 15ed15a allows remote attackers to crash reverse-proxy servers via HTTP/3 cancellation. The shutdown_stream function in lib/http3/server.c stops the QUIC receive side without unlinking the canceled stream from the pending-stream list, leaving stale state that reaches an assertion. Exploitation requires HTTP/3 and reverse-proxy mode; the standalone server normally restarts, but concurrent requests are interrupted.

The record

CVE
CVE-2024-45403
Published
Oct 11, 2024
Updated
Oct 11, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-617, T1499
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

3.7GitHubCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

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.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-617Reachable Assertion
T1499Endpoint Denial of Service

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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