CVE-2026-12523Network attack vector

Service interruption via attacker-controlled frame allocation

Published Jul 14, 2026 · Updated Jul 14, 2026

Resource exhaustion in Cloudflare quiche before 0.29.3 allows remote attackers to interrupt service via crafted HTTP/3 frames. The HTTP/3 parser preallocates memory from declared frame lengths before receiving their payloads, while QPACK handling fails to enforce MAX_FIELD_SECTION_SIZE during HEADERS decompression. An unauthenticated network peer can force memory commitment without sending the declared payload, exhausting process memory and disrupting any application embedding the library.

CVSS severity7.5
High
EPSS probability0.53%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Resource exhaustion in Cloudflare quiche before 0.29.3 allows remote attackers to interrupt service via crafted HTTP/3 frames. The HTTP/3 parser preallocates memory from declared frame lengths before receiving their payloads, while QPACK handling fails to enforce MAX_FIELD_SECTION_SIZE during HEADERS decompression. An unauthenticated network peer can force memory commitment without sending the declared payload, exhausting process memory and disrupting any application embedding the library.

The record

CVE
CVE-2026-12523
Published
Jul 14, 2026
Updated
Jul 14, 2026
Vendor
Cloudflare
Product
quiche
Classifications
CWE-400, T1499.003
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 14, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.1.0 <0.29.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Cloudflare · quicheversion=0.1.0 <0.29.3

Published CVSS scores

7.5CloudflareCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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-400Uncontrolled Resource Consumption
T1499.003Application Exhaustion Flood

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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