CVE-2026-12523: cloudflare quiche Uncontrolled Resource Consumption

Vulnerability summary

CVE-2026-12523 is a high (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in cloudflare quiche. EPSS estimates a 0.53% chance of exploitation in the next 30 days, higher than 44.1% of scored vulnerabilities.

Timeline

1. 14-07-2026
   PublishedVulnerability first disclosed.
2. 15-07-2026
   Last modifiedVulnerability information updated.

Description

Summary Cloudflare quiche's HTTP/3 layer was discovered to be vulnerable to resource exhaustion (i.e., memory) by means of specially crafted HTTP/3 frames. Impact HTTP/3 defines multiple frame types to support HTTP message exchanges and connection management. Each frame has a length and a payload whose length depends on the frame type. quiche was found to be vulnerable when parsing some frame types to pre-allocating memory based on the declared length. An attacker would not need to send the number of declared bytes to trigger this issue. In addition, quiche was found to not apply QPACK decompression limits correctly. This could allow an attacker to send specially crafted HEADERS frames that would cause more memory commitment than otherwise advertised by MAX_FIELD_SECTION_SIZE (configured by set_max_field_section_size()). Mitigation: * Users are requested to upgrade to quiche 0.29.3 which is the earliest version containing the fix for this issue. Credits: Disclosed responsibly by Sébastien Féry

• CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.