CVE-2017-9798

CVE-2017-9798 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 95% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-416.

Key facts

Description

Apache httpd allows remote attackers to read secret data from process memory if the Limit directive can be set in a user's .htaccess file, or if httpd.conf has certain misconfigurations, aka Optionsbleed. This affects the Apache HTTP Server through 2.2.34 and 2.4.x through 2.4.27. The attacker sends an unauthenticated OPTIONS HTTP request when attempting to read secret data. This is a use-after-free issue and thus secret data is not always sent, and the specific data depends on many factors including configuration. Exploitation with .htaccess can be blocked with a patch to the ap_limit_section function in server/core.c.

Frequently asked questions

What is CVE-2017-9798?
Apache httpd allows remote attackers to read secret data from process memory if the Limit directive can be set in a user's .htaccess file, or if httpd.conf has certain misconfigurations, aka Optionsbleed. This affects the Apache HTTP Server through 2.2.34 and 2.4.x through 2.4.27. The attacker sends an unauthenticated OPTIONS HTTP request when attempting to read secret data. This is a use-after-free issue and thus secret data is not always sent, and the specific data depends on many factors including configuration. Exploitation with .htaccess can be blocked with a patch to the ap_limit_section function in server/core.c.
How severe is CVE-2017-9798?
CVE-2017-9798 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 high, integrity none, and availability none.
Is CVE-2017-9798 being actively exploited?
It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 95% (100th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2017-9798?
CVE-2017-9798 primarily affects Apache Http Server. In total, 22 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2017-9798?
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-2017-9798 published?
CVE-2017-9798 was published on 2017-09-18 and last updated on 2026-06-17.

References

Affected products (22)

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Threat intelligence

Threat-intel indicators referencing this CVE: