How severe is CVE-2017-9798?

CVE-2017-9798 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2017-9798?

Affected package information for CVE-2017-9798 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2017-9798?

Upgrade the affected component to the fixed release for CVE-2017-9798, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.

How do I detect CVE-2017-9798 in my code and dependencies?

Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

How do I mitigate CVE-2017-9798 if there is no patch (or I can't update yet)?

Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Is CVE-2017-9798 actively exploited in the wild?

Yes. There are 12 known exploit references for CVE-2017-9798, including 1 documented proof-of-concept exploit on Exploit-DB and 8 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2017-9798?

CVE-2017-9798 has an EPSS (Exploit Prediction Scoring System) score of 95.0%, placing it in the 100th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

What type of vulnerability is CVE-2017-9798?

CVE-2017-9798 is classified as Use After Free (CWE-416). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2017-9798 published, and has it been updated?

CVE-2017-9798 was published on September 18, 2017 and was last updated on October 20, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🛡️

Not in CISA KEV

HIGH severity

CVE-2017-9798 — httpd

HIGHFix: apache/httpd@4cc2782

CVE-2017-9798 is a high-severity (CVSS 7.5) Use After Free vulnerability. 12 public exploit references exist, so weaponization risk is real. A fix is available — see the affected versions and patch details below.

Published

Sep 18, 2017

Updated

Oct 20, 2026

Affected

2 products

Patched

See advisory

Exploits

12 known

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

95.0%probability of exploitation in next 30 days

Very High Risk0.00%

Lower risk than most CVEs100th percentile — riskier than 100% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2017-9798 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 394,803 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.

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.

Affected Products

2 products · 22 configurations

Application

http serverapache

≤ 2.2.34

18 versions

2.4.02.4.12.4.22.4.32.4.42.4.62.4.72.4.92.4.102.4.122.4.162.4.17

debian linuxdebian

3 versions

7.08.09.0

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-42745webappslinux

Apache < 2.2.34 / < 2.4.27 - OPTIONS Memory Leak

by Hanno Bock · Sep 18, 2017

Exploit-DB Source

Detection & mitigation playbook

Vulnerability

Detect
Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).
Fix
Upgrade the affected component to the fixed release for CVE-2017-9798, or apply your distribution's backported patch — distro builds are often patched at an older version number, so check your vendor's advisory rather than the upstream version alone.
Workarounds
Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatModerate

This issue affects the versions of httpd as shipped with Red Hat Enterprise Linux 5, 6, and 7. This issue affects the versions of httpd24-httpd as shipped with Red Hat Software Collections. Product Security has rated this issue as having Moderate security impact. In order to be vulnerable, .htaccess files need to…

Workaround published by Red Hat

This issue can be mitigated by configuring httpd to disallow the use of the "Limit" configuration directive in .htaccess files. The set of directives that can be used in .htaccess files is configured using the "AllowOverride" directive. Refer to Red Hat Bugzilla bug 1490344 for further details: https://bugzilla.redhat.com/show_bug.cgi?id=1490344#c18

Source: Red Hat security advisory for CVE-2017-9798 (CC BY 4.0)

Product	Fixed in	Advisory
JBoss Core Services on RHEL 6	`jbcs-httpd24-httpd-0:2.4.23-125.jbcs.el6`	RHSA-2017:3477
JBoss Core Services on RHEL 7	`jbcs-httpd24-httpd-0:2.4.23-125.jbcs.el7`	RHSA-2017:3476
Red Hat Enterprise Linux 6	`httpd-0:2.2.15-60.el6_9.6`	RHSA-2017:2972
Red Hat Enterprise Linux 6.7 Extended Update Support	`httpd-0:2.2.15-47.el6_7.5`	RHSA-2017:3195
Red Hat Enterprise Linux 7	`httpd-0:2.4.6-67.el7_4.5`	RHSA-2017:2882
Red Hat Enterprise Linux 7.2 Extended Update Support	`httpd-0:2.4.6-40.el7_2.6`	RHSA-2017:3193
Red Hat Enterprise Linux 7.3 Extended Update Support	`httpd-0:2.4.6-45.el7_3.5`	RHSA-2017:3194
Red Hat JBoss Core Services	`httpd`	RHSA-2017:3475

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