cbcvebase.
CVE-2017-9798
published 2017-09-18

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…

PriorityP185high7.5CVSS 3.1
AVNACLPRNUINSUCHINAN
ITWEXPLOITVulnCheck KEVRansomwareInitial access
Exploited in the wild
EPSS
95.00%
99.9th percentile
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

26 ranges· showing 25
VendorProductVersion rangeFixed in
apachehttp_server<= 2.2.34
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttp_server
apachehttpd
apache_software_foundationapache_http_server
applemacos_high_sierra_10.13.2_security_update_2017-002_sierra_and_security_update_20
debianapache2< apache2 2.4.27-6 (bookworm)apache2 2.4.27-6 (bookworm)
debiandebian_linux
debiandebian_linux

Detection & IOCsextracted from sources · hover to see the quote

commandcurl -sI -X OPTIONS http://{IP address}/test/index.html
commandcurl -sI -X ANYANY http://192.168.93.207/test/index.html
pathserver/core.c
  • Detect exploitation attempts by monitoring for HTTP OPTIONS requests or requests with unknown/arbitrary HTTP methods that elicit an Allow header in the response — both can trigger the memory leak.
  • Any HTTP request that forces the server to send an Allow header (e.g., a 501 Method Not Implemented response to an unknown method) can trigger the vulnerability — not just OPTIONS requests.
  • Inspect HTTP responses for anomalous or garbled data appended to the Allow header beyond standard method names — this is the indicator of memory being leaked via the use-after-free bug.
  • The leak can repeat and grow with successive requests; monitor for repeated unauthenticated OPTIONS or unknown-method requests to the same resource as a behavioral indicator of active exploitation.
  • ·The vulnerability only triggers if the Limit directive is set in a .htaccess file with an invalid/custom HTTP method, OR if httpd.conf has certain misconfigurations — servers without such configurations are not affected.
  • ·The patch restricts the Limit directive to httpd.conf only (disallowing it in .htaccess) and only adds new methods when cmd->temp_pool equals cmd->pool — detection rules targeting .htaccess-based exploitation will not apply to patched servers.

CVSS provenance

nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
nvdv2.05.0MEDIUMAV:N/AC:L/Au:N/C:P/I:N/A:N
osv7.5HIGH
vulncheck7.5HIGH
vendor_apache7.5LOW
vendor_debian7.5HIGH
vendor_redhat7.5HIGH
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