How severe is CVE-2023-30847?

CVE-2023-30847 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability high.

Is CVE-2023-30847 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2023-30847?

CVE-2023-30847 primarily affects Dena H2o. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2023-30847?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2023-30847 published?

CVE-2023-30847 was published on 2023-04-27 and last updated on 2026-06-17.

CVE-2023-30847

CVE-2023-30847 is a high-severity vulnerability in Dena H2o with a CVSS 3.x base score of 8.2. 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-824.

Key facts

Severity: High (CVSS 3.x base score 8.2)
EPSS exploit prediction: 1% (55th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-824
Affected product: Dena H2o
Published: 2023-04-27
Last modified: 2026-06-17

Description

H2O is an HTTP server. In versions 2.3.0-beta2 and prior, when the reverse proxy handler tries to processes a certain type of invalid HTTP request, it tries to build an upstream URL by reading from uninitialized pointer. This behavior can lead to crashes or leak of information to back end HTTP servers. Pull request number 3229 fixes the issue. The pull request has been merged to the `master` branch in commit f010336. Users should upgrade to commit f010336 or later.

Frequently asked questions

What is CVE-2023-30847?: H2O is an HTTP server. In versions 2.3.0-beta2 and prior, when the reverse proxy handler tries to processes a certain type of invalid HTTP request, it tries to build an upstream URL by reading from uninitialized pointer. This behavior can lead to crashes or leak of information to back end HTTP servers. Pull request number 3229 fixes the issue. The pull request has been merged to the `master` branch in commit f010336. Users should upgrade to commit f010336 or later.
How severe is CVE-2023-30847?: CVE-2023-30847 has a CVSS 3.x base score of 8.2, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability high.
Is CVE-2023-30847 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (55th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2023-30847?: CVE-2023-30847 primarily affects Dena H2o. In total, 3 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2023-30847?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2023-30847 published?: CVE-2023-30847 was published on 2023-04-27 and last updated on 2026-06-17.

References

Affected products (3)

cpe:2.3:a:dena:h2o:*:*:*:*:*:*:*:*
cpe:2.3:a:dena:h2o:2.3.0:beta1:*:*:*:*:*:*
cpe:2.3:a:dena:h2o:2.3.0:beta2:*:*:*:*:*:*

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-2023-44487 — 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…
CVE-2017-10868 — High (CVSS 7.5): H2O version 2.2.2 and earlier allows remote attackers to cause a denial of service in the server via specially crafted…

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Other CWE-824 vulnerabilities

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CVE-2026-2805 — Critical (CVSS 9.8): Invalid pointer in the DOM: Core & HTML component. This vulnerability was fixed in Firefox 148 and Thunderbird 148.
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CVE-2022-46280 — Critical (CVSS 9.8): A use of uninitialized pointer vulnerability exists in the PQS format pFormat functionality of Open Babel 3.1.1 and…
CVE-2022-44451 — Critical (CVSS 9.8): A use of uninitialized pointer vulnerability exists in the MSI format atom functionality of Open Babel 3.1.1 and master…

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