How severe is CVE-2024-45403?

CVE-2024-45403 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2024-45403 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2024-45403?

CVE-2024-45403 affects Dena H2o. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2024-45403?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2024-45403 have an EU (EUVD) identifier?

Yes. CVE-2024-45403 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-41461.

When was CVE-2024-45403 published?

CVE-2024-45403 was published on 2024-10-11 and last updated on 2026-06-17.

CVE-2024-45403

CVE-2024-45403 is a low-severity vulnerability in Dena H2o with a CVSS 3.x base score of 3.7. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-617.

Key facts

Severity: Low (CVSS 3.x base score 3.7)
EPSS exploit prediction: 1% (46th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2024-41461
Weakness: CWE-617
Affected product: Dena H2o
Published: 2024-10-11
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2024-45403?: 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.
How severe is CVE-2024-45403?: CVE-2024-45403 has a CVSS 3.x base score of 3.7, rated low severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2024-45403 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (46th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2024-45403?: CVE-2024-45403 affects Dena H2o. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2024-45403?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2024-45403 have an EU (EUVD) identifier?: Yes. CVE-2024-45403 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2024-41461.
When was CVE-2024-45403 published?: CVE-2024-45403 was published on 2024-10-11 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:dena:h2o:*:*:*:*:*:*:*:*

More vulnerabilities in Dena H2o

CVE-2018-0608 — Critical (CVSS 9.8): Buffer overflow in H2O version 2.2.4 and earlier allows remote attackers to execute arbitrary code or cause a denial of…
CVE-2016-7835 — Critical (CVSS 9.1): Use-after-free vulnerability in H2O allows remote attackers to cause a denial-of-service (DoS) or obtain server…
CVE-2023-30847 — High (CVSS 8.2): H2O is an HTTP server. In versions 2.3.0-beta2 and prior, when the reverse proxy handler tries to processes a certain…
CVE-2023-44487 — High (CVSS 7.5): The HTTP/2 protocol allows a denial of service (server resource consumption) because request cancellation can reset…
CVE-2017-10908 — High (CVSS 7.5): H2O version 2.2.3 and earlier allows remote attackers to cause a denial of service in the server via specially crafted…
CVE-2017-10869 — High (CVSS 7.5): Buffer overflow in H2O version 2.2.2 and earlier allows remote attackers to cause a denial-of-service in the server via…

All CVEs affecting Dena H2o →

Other CWE-617 (Reachable Assertion) vulnerabilities

CVE-2020-3615 — Critical (CVSS 9.8): Valid deauth/disassoc frames is dropped in case if RMF is enabled and some rouge peer keep on sending rogue…
CVE-2019-9795 — Critical (CVSS 9.8): A vulnerability where type-confusion in the IonMonkey just-in-time (JIT) compiler could potentially be used by…
CVE-2026-31739 — High (CVSS 8.8): In the Linux kernel, the following vulnerability has been resolved: crypto: tegra - Add missing CRYPTO_ALG_ASYNC The…
CVE-2020-12417 — High (CVSS 8.8): Due to confusion about ValueTags on JavaScript Objects, an object may pass through the type barrier, resulting in…
CVE-2020-6623 — High (CVSS 8.8): stb stb_truetype.h through 1.22 has an assertion failure in stbtt__cff_get_index.
CVE-2020-6619 — High (CVSS 8.8): stb stb_truetype.h through 1.22 has an assertion failure in stbtt__buf_seek.

Browse all CWE-617 (Reachable Assertion) vulnerabilities →