CVE-2023-50247Network attack vector

Service abort via unbounded QUIC response queue

Published Dec 12, 2023 · Updated Aug 2, 2024

State exhaustion in h2o 2.3.0-beta2 and earlier allows remote attackers to abort HTTP/3 service through crafted QUIC traffic. In deps/quicly/lib/quicly.c, each received PATH_CHALLENGE schedules a separately heap-allocated PATH_RESPONSE node without bounding the pending queue, so retained connection state grows with repeated frames. The attack requires HTTP/3 to be enabled; HTTP/1 and HTTP/2 do not use QUIC and are unaffected, and exhaustion ends in a process abort rather than data disclosure or modification.

CVSS severity3.7
Low
EPSS probability0.86%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

State exhaustion in h2o 2.3.0-beta2 and earlier allows remote attackers to abort HTTP/3 service through crafted QUIC traffic. In deps/quicly/lib/quicly.c, each received PATH_CHALLENGE schedules a separately heap-allocated PATH_RESPONSE node without bounding the pending queue, so retained connection state grows with repeated frames. The attack requires HTTP/3 to be enabled; HTTP/1 and HTTP/2 do not use QUIC and are unaffected, and exhaustion ends in a process abort rather than data disclosure or modification.

The record

CVE
CVE-2023-50247
Published
Dec 12, 2023
Updated
Aug 2, 2024
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-770, T1499.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 12, 2023CVE publishedPublication date reported by the CVE source.
  2. Aug 2, 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 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-770Allocation of Resources Without Limits or Throttling
T1499.002Service Exhaustion Flood

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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