CVE-2016-8740

CVE-2016-8740 is a high-severity vulnerability in Apache Http Server with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 79% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-20.

Key facts

Description

The mod_http2 module in the Apache HTTP Server 2.4.17 through 2.4.23, when the Protocols configuration includes h2 or h2c, does not restrict request-header length, which allows remote attackers to cause a denial of service (memory consumption) via crafted CONTINUATION frames in an HTTP/2 request.

Frequently asked questions

What is CVE-2016-8740?
The mod_http2 module in the Apache HTTP Server 2.4.17 through 2.4.23, when the Protocols configuration includes h2 or h2c, does not restrict request-header length, which allows remote attackers to cause a denial of service (memory consumption) via crafted CONTINUATION frames in an HTTP/2 request.
How severe is CVE-2016-8740?
CVE-2016-8740 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2016-8740 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 79% (100th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2016-8740?
CVE-2016-8740 primarily affects Apache Http Server. In total, 7 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2016-8740?
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-2016-8740 published?
CVE-2016-8740 was published on 2016-12-05 and last updated on 2026-06-17.

References

Affected products (7)

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Threat intelligence

Threat-intel indicators referencing this CVE: