CVE-2026-12523
Resource exhaustion in quiche HTTP/3 and QPACK layers
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
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
Resource exhaustion in quiche HTTP/3 and QPACK layers
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
- Record
CVE-2026-12523- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-400
- Updated
- 2026-11-02
EUVDEUVD-2026-43748
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
- Record
EUVD-2026-43748- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
NVD
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
- Record
CVE-2026-12523- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-400
- Updated
- 2026-11-02
OSV
Resource exhaustion in quiche HTTP/3 and QPACK layers
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
- Record
CVE-2026-12523- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Public exploits
Links only. Every CVE stores no exploit code.
| Source | Link | Date |
|---|---|---|
| PoC in GitHub | HORKimhab/CVE-2025-64702-more | 2026-10-22 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, NVD, OSV, PoC in GitHub |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-12523 is a high vulnerability (CVSS 7.5) in Cloudflare Quiche, published July 14, 2026. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 0.53%, the 45th percentile. No source names a fixed version.