Use After Free in Apache HTTP Server
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.
Vulnerability class: Use-After-Free
EPSS: 0.950 (99.9th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N.
Affected products
- Apache Http_server — versions 2.4.0, 2.4.1, 2.4.2
- Apache Software Foundation Http Server — versions Apache HTTP Server through 2.2.34 and 2.4.x through 2.4.27
- Debian Debian_linux — versions 7.0, 8.0, 9.0
Weakness classification (CWE)
Public proof-of-concept exploits
References
- security@apache.org (x_refsource_REDHAT, vendor-advisory, Third Party Advisory)
- security@apache.org (VDB Entry, Third Party Advisory, vdb-entry, x_refsource_BID)
- security@apache.org (x_refsource_CONFIRM, Patch, Third Party Advisory)
- security@apache.org (x_refsource_CONFIRM, Patch, Third Party Advisory)
- security@apache.org (x_refsource_CONFIRM, Patch, Third Party Advisory)
- security@apache.org (x_refsource_REDHAT, vendor-advisory, Third Party Advisory)
- security@apache.org (x_refsource_REDHAT, vendor-advisory, Third Party Advisory)
- security@apache.org (Technical Description, Exploit, Patch, Third Party Advisory, x_refsource_MISC)
- security@apache.org (x_refsource_CONFIRM, Third Party Advisory)
- security@apache.org (VDB Entry, Third Party Advisory, vdb-entry, x_refsource_SECTRACK)
Frequently asked questions
- What is CVE-2017-9798?
- CVE-2017-9798 is a high-severity vulnerability in Apache HTTP Server, classified under Use After Free. CVSS score: 7.5/10. Published 2017-09-18.
- How severe is CVE-2017-9798?
- High severity. CVSS v3 base score is 7.5 out of 10.
- Is CVE-2017-9798 known to be exploited?
- 54 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.