CVE-2024-45403
H2O assertion failure when HTTP/3 requests are cancelled
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. When h2o is configured as a reverse proxy and HTTP/3 requests are cancelled by the client, h2o might crash due to an assertion failure. The crash can be exploited by an attacker to mount a Denial-of-Service attack. By default, the h2o standalone server automatically restarts, minimizing the impact. However, HTTP requests that were served concurrently will still be disrupted. The vulnerability has been addressed in commit 1ed32b2. Users may disable the use of HTTP/3 to mitigate the issue.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
3.7
H2O assertion failure when HTTP/3 requests are cancelled
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. When h2o is configured as a reverse proxy and HTTP/3 requests are cancelled by the client, h2o might crash due to an assertion failure. The crash can be exploited by an attacker to mount a Denial-of-Service attack. By default, the h2o standalone server automatically restarts, minimizing the impact. However, HTTP requests that were served concurrently will still be disrupted. The vulnerability has been addressed in commit 1ed32b2. Users may disable the use of HTTP/3 to mitigate the issue.
- Record
CVE-2024-45403- CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-617
- Updated
- 2026-11-02
EUVDEUVD-2024-41461
3.7
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. When h2o is configured as a reverse proxy and HTTP/3 requests are cancelled by the client, h2o might crash due to an assertion failure. The crash can be exploited by an attacker to mount a Denial-of-Service attack. By default, the h2o standalone server automatically restarts, minimizing the impact. However, HTTP requests that were served concurrently will still be disrupted. The vulnerability has been addressed in commit 1ed32b2. Users may disable the use of HTTP/3 to mitigate the issue.
- Record
EUVD-2024-41461- CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-03
NVD
3.7
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. When h2o is configured as a reverse proxy and HTTP/3 requests are cancelled by the client, h2o might crash due to an assertion failure. The crash can be exploited by an attacker to mount a Denial-of-Service attack. By default, the h2o standalone server automatically restarts, minimizing the impact. However, HTTP requests that were served concurrently will still be disrupted. The vulnerability has been addressed in commit 1ed32b2. Users may disable the use of HTTP/3 to mitigate the issue.
- Record
CVE-2024-45403- CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L - 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-617
- Updated
- 2026-11-02
OSV
3.7
H2O assertion failure when HTTP/3 requests are cancelled
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. When h2o is configured as a reverse proxy and HTTP/3 requests are cancelled by the client, h2o might crash due to an assertion failure. The crash can be exploited by an attacker to mount a Denial-of-Service attack. By default, the h2o standalone server automatically restarts, minimizing the impact. However, HTTP requests that were served concurrently will still be disrupted. The vulnerability has been addressed in commit 1ed32b2. Users may disable the use of HTTP/3 to mitigate the issue.
- Record
CVE-2024-45403- CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-617
- Updated
- 2026-11-02
OSVUBUNTU-CVE-2024-45403
3.7
h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. When h2o is configured as a reverse proxy and HTTP/3 requests are cancelled by the client, h2o might crash due to an assertion failure. The crash can be exploited by an attacker to mount a Denial-of-Service attack. By default, the h2o standalone server automatically restarts, minimizing the impact. However, HTTP requests that were served concurrently will still be disrupted. The vulnerability has been addressed in commit 1ed32b2. Users may disable the use of HTTP/3 to mitigate the issue.
- Record
UBUNTU-CVE-2024-45403- CVSS 3.1
- 3.7 Low
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L - 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
Affected packages
| Package | Affected | Fixed |
|---|---|---|
h2oUbuntu:Pro:18.04:LTS |
All versions, plus listed versions 2.2.3+dfsg-22.2.4+dfsg-12.2.4+dfsg-1build12.2.4+dfsg-1ubuntu0.1~esm2 |
None known |
h2oUbuntu:Pro:20.04:LTS |
All versions, plus listed versions 2.2.5+dfsg2-32.2.5+dfsg2-3build12.2.5+dfsg2-3ubuntu0.1~esm1 |
None known |
h2oUbuntu:Pro:22.04:LTS |
All versions, plus listed versions 2.2.5+dfsg2-62.2.5+dfsg2-6.12.2.5+dfsg2-6.1ubuntu12.2.5+dfsg2-6.1ubuntu22.2.5+dfsg2-6.1ubuntu2+esm1 |
None known |
h2oUbuntu:24.04:LTS |
All versions, plus listed versions 2.2.5+dfsg2-72.2.5+dfsg2-82.2.5+dfsg2-8.1ubuntu12.2.5+dfsg2-8.1ubuntu22.2.5+dfsg2-8.1ubuntu3 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases, published | EUVD | |
| first indexed | CVE List, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2024-45403 is a low vulnerability (CVSS 3.7) in Dena H2o, published October 11, 2024. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.65%, the 51st percentile. No source names a fixed version.
References
github.com/h2o/h2o/security/advisories/GHSA-4xp5-3jhc-3m92
github.com/h2o/h2o/commit/16b13eee8ad7895b4fe3fcbcabee53bd52782562
github.com/h2o/h2o/commit/1ed32b23f999acf0c5029f09c8525f93eb1d354c
h2o.examp1e.net/configure/http3_directives.html
github.com/CVEProject/cvelistV5/tree/main/cves/2024/45xxx/CVE-2024-45403.json
nvd.nist.gov/vuln/detail/CVE-2024-45403
ubuntu.com/security/CVE-2024-45403
cve.org/CVERecord?id=CVE-2024-45403