cbcvebase.
CVE-2014-6271
published 2014-09-24

CVE-2014-6271: GNU Bash through 4.3 processes trailing strings after function definitions in the values of environment variables, which allows remote attackers to execute…

PriorityP195critical9.8CVSS 3.1
AVNACLPRNUINSUCHIHAH
KEVITWEXPLOITInitial access
CISA Known Exploited Vulnerabilitydue 2022-07-28
Exploited in the wild
EPSS
100.00%
100.0th percentile
GNU Bash through 4.3 processes trailing strings after function definitions in the values of environment variables, which allows remote attackers to execute arbitrary code 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, aka "ShellShock." NOTE: the original fix for this issue was incorrect; CVE-2014-7169 has been assigned to cover the vulnerability that is still present after the incorrect fix.

Affected

286 ranges· showing 25
VendorProductVersion rangeFixed in
applemac_os_x>= 10.0.0 < 10.10.010.10.0
aristaeos>= 4.10.0 < 4.10.94.10.9
aristaeos>= 4.11.0 < 4.11.114.11.11
aristaeos>= 4.12.0 < 4.12.94.12.9
aristaeos>= 4.13.0 < 4.13.94.13.9
aristaeos>= 4.14.0 < 4.14.4f4.14.4f
aristaeos>= 4.9.0 < 4.9.124.9.12
canonicalubuntu_linux
canonicalubuntu_linux
canonicalubuntu_linux
checkpointsecurity_gateway< r77.30r77.30
citrixcitrix_adm
citrixcitrix_hypervisor
citrixcitrix_netscaler_adc
citrixcitrix_netscaler_sdx
citrixcitrix_virtual_apps_and_desktops
citrixcitrix_xenapp
citrixcitrix_xendesktop
citrixcitrix_xenmobile
citrixcitrix_xenserver
citrixendpoint_management
citrixnetscaler_adc
citrixnetscaler_gateway
citrixnetscaler_sdx
citrixnetscaler_sdx_firmware< 9.3.67.5r19.3.67.5r1

Detection & IOCsextracted from sources · hover to see the quote

path/cgi-bin/count.cgi
path/cgi-sys/defaultwebpage.cgi
path/cgi-bin/test.sh
path/cgi-bin/test.cgi
path/cgi-bin/test-cgi
path/cgi-bin/help.cgi
other() { :; };
snort
SIDs 31975-31978, 31985
bytes
() {
  • Detect Shellshock exploit attempts by inspecting HTTP headers (User-Agent, Referer, Cookie, etc.) for the pattern '() {' which indicates a malicious Bash function injection attempt.
  • Monitor web server logs and CGI paths for probing of common vulnerable endpoints such as /cgi-bin/test.cgi, /cgi-bin/test-cgi, /cgi-sys/defaultwebpage.cgi, and /cgi-bin/count.cgi.
  • Detect ELF malware dropped to /tmp/ (e.g., /tmp/syslogd) with world-executable permissions (chmod 777) following a wget download, a common post-exploitation pattern in Shellshock attacks.
  • Scan for ClamAV signature 'Linux.Flooder.Agent' on ELF binaries observed being downloaded to vulnerable targets via wget in Shellshock exploitation campaigns.
  • Detect Shellshock exploitation attempts using Sourcefire/Snort SIDs 31975-31978 and 31985, and Cisco IPS signatures 4689-0 through 4689-3.
  • Monitor for crontab modifications on web servers following exploitation, as attackers establish persistence by scheduling weekly re-download and re-infection of the malicious payload.
  • Detect Shellshock exploitation attempts involving Base64-encoded payloads delivered via HTTP, used to evade signature-based detection of Perl IRC bots.
  • Alert on use of the 'shred' command followed by file deletion on web servers, a stealth technique used by Shellshock attackers to remove evidence of dropped shell scripts.
  • ·The initial Bash patches for CVE-2014-6271 were found to be incomplete; follow-on CVEs (CVE-2014-7169, CVE-2014-6277, CVE-2014-6278) represent bypasses. Detection signatures must cover all variants.
  • ·Shellshock affects more than port 80; Shodan data showing 3515 vulnerable devices on port 80 is likely a significant undercount of the true exposure across all ports.
  • ·Scanning source IPs may be benign researchers rather than malicious actors; distinguishing malicious from non-malicious scans based on IP alone is not always possible.
  • ·Nessus remote detection of Shellshock relies on a vulnerable service calling Bash; LCE process accounting provides complementary detection via a different method.

CVSS provenance

nvdv3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
nvdv2.010.0CRITICALAV:N/AC:L/Au:N/C:C/I:C/A:C
osv9.8CRITICAL
vulncheck9.8CRITICAL
cisa9.8CRITICAL
vendor_debian9.8CRITICAL
vendor_redhat9.8CRITICAL
vendor_cisco7.5HIGH
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