cbcvebase.
CVE-2015-7547
published 2016-02-18

CVE-2015-7547: Multiple stack-based buffer overflows in the (1) send_dg and (2) send_vc functions in the libresolv library in the GNU C Library (aka glibc or libc6) before…

PriorityP187high8.1CVSS 3.0
AVNACHPRNUINSUCHIHAH
ITWEXPLOITVulnCheck KEVInitial access
Exploited in the wild
EPSS
89.56%
99.8th percentile
Multiple stack-based buffer overflows in the (1) send_dg and (2) send_vc functions in the libresolv library in the GNU C Library (aka glibc or libc6) before 2.23 allow remote attackers to cause a denial of service (crash) or possibly execute arbitrary code via a crafted DNS response that triggers a call to the getaddrinfo function with the AF_UNSPEC or AF_INET6 address family, related to performing "dual A/AAAA DNS queries" and the libnss_dns.so.2 NSS module.

Affected

65 ranges· showing 25
VendorProductVersion rangeFixed in
canonicalubuntu_linux
canonicalubuntu_linux
canonicalubuntu_linux
debiandebian_linux
debianglibc< glibc 2.21-8 (bookworm)glibc 2.21-8 (bookworm)
f5big-ip_access_policy_manager
f5big-ip_advanced_firewall_manager
f5big-ip_analytics
f5big-ip_application_acceleration_manager
f5big-ip_application_security_manager
f5big-ip_domain_name_system
f5big-ip_link_controller
f5big-ip_local_traffic_manager
f5big-ip_policy_enforcement_manager
gnuglibc
gnuglibc
gnuglibc
gnuglibc
gnuglibc
gnuglibc
gnuglibc
gnuglibc
gnuglibc
gnuglibc
gnuglibc

Detection & IOCsextracted from sources · hover to see the quote

command\x48\x31\xff\x57\x57\x5e\x5a\x48\xbf\x2f\x2f\x62\x69\x6e\x2f\x73\x68\x48\xc1\xef\x08\x57\x54\x5f\x6a\x3b\x58\x0f\x05
filenamelibnss_dns.so.2
bytes
\x90 * 1955 (NOP sled) followed by /bin/sh shellcode
bytes
DNS flags 0x8380 (response with truncated bit set)
  • Detect oversized DNS responses (>2048 bytes) triggering TCP fallback (truncated bit set in UDP response followed by TCP DNS query to same server) — characteristic of CVE-2015-7547 exploitation attempt.
  • Monitor for dual A/AAAA DNS queries (AF_UNSPEC or AF_INET6) to the same hostname that receive anomalously large responses (>2048 bytes), especially with the truncated flag set in UDP forcing TCP retry.
  • In exploit PoC, the malicious DNS server sends a UDP response with truncated flag (0x8380) and a padding of 2500 null bytes to force malloc, then delivers the overflow payload over TCP — alert on DNS UDP responses with TC=1 and anomalous padding.
  • Alert on DNS TCP responses containing large NOP sleds (0x90 repeated hundreds/thousands of times) followed by x86-64 execve /bin/sh shellcode bytes.
  • The exploit requires the attacker to control the DNS server configured on the victim. Detect DNS resolution directed at untrusted/external DNS servers not in the approved resolver list, especially for privileged processes (sshd, sudo, curl, apache).
  • Monitor for DNS responses with an unusually high answer count (PoC uses 184 answers) in a single response, which is anomalous and indicative of exploitation.
  • ·Exploitation requires the attacker to control the DNS server configured on the target device; the vulnerability is not exploitable via arbitrary network positions without DNS server control.
  • ·Additional anti-exploitation mitigations such as ASLR must be overcome for successful code execution; crash/DoS is more reliably achievable.
  • ·The PoC server code will crash any client on the same system that calls getaddrinfo() while testing is underway, not just the intended target process.
  • ·RedHat-listed mitigations (e.g., DNS response size limits) have the potential to interfere with normal DNS operations and should only be applied if DNS usage is well understood.

CVSS provenance

nvdv3.08.1HIGHCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
nvdv2.06.8MEDIUMAV:N/AC:M/Au:N/C:P/I:P/A:P
osv8.1HIGH
vulncheck8.1HIGH
vendor_debian8.1HIGH
vendor_redhat8.1HIGH
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