- What is the severity of CVE-2023-4911?
- CVE-2023-4911 has been scored as a high severity vulnerability.
- How to fix CVE-2023-4911?
- As a workaround for remediating CVE-2023-4911: For customers who cannot update immediately and do not have Secure Boot feature enabled, the issue can be mitigated using the provided SystemTap script with the following steps. When enabled, any setuid program invoked with GLIBC_TUNABLES in the environment will be terminated immediately. To invoke the setuid program, users will then have to unset or clear the GLIBC_TUNABLES envvar, e.g. `GLIBC_TUNABLES= sudo` . Note that these mitigation steps will need to be repeated if the system is rebooted. 1) Install required systemtap packages and dependencies as per - https://access.redhat.com/solutions/5441 2) Create the following systemtap script, and name it stap_block_suid_tunables.stp: ~~~ function has_tunable_string:long() { name = "GLIBC_TUNABLES" mm = @task(task_current())->mm; if (mm) { env_start = @mm(mm)->env_start; env_end = @mm(mm)->env_end; if (env_start != 0 && env_end != 0) while (env_end > env_start) { cur = user_string(env_start, ""); env_name = tokenize(cur, "="); if (env_name == name && tokenize("", "") != "") return 1; env_start += strlen (cur) + 1 } } return 0; } probe process("/lib*/ld*.so*").function("__tunables_init") { atsecure = 0; /* Skip processing if we can't read __libc_enable_secure, e.g. core dump handler (systemd-cgroups-agent and systemd-coredump). */ try { atsecure = @var("__libc_enable_secure"); } catch { printk (4, sprintf ("CVE-2023-4911: Skipped check: %s (%d)", execname(), pid())); } if (atsecure && has_tunable_string ()) raise (9); } ~~~ 3) Load the systemtap module into the running kernel: ~~~ stap -g -F -m stap_block_suid_tunables stap_block_suid_tunables.stp ~~~ 4) Ensure the module is loaded: ~~~ lsmod | grep -i stap_block_suid_tunables stap_block_suid_tunables 249856 0 ~~~ 5) Once the glibc package is updated to the version containing the fix, the systemtap generated kernel module can be removed by running: ~~~ rmmod stap_block_suid_tunables ~~~ If Secure Boot is enabled on a system, the SystemTap module must be signed. An external compiling server can be used to sign the generated kernel module with a key enrolled into the kernel's keyring or starting with SystemTap 4.7 you can sign a module without a compile server. See further information here - https://www.redhat.com/sysadmin/secure-boot-systemtap
- Is CVE-2023-4911 being actively exploited in the wild?
- It is confirmed that CVE-2023-4911 is actively exploited. Be extra cautious if you are using vulnerable components. According to its EPSS score, there is a ~79% probability that this vulnerability will be exploited by malicious actors in the next 30 days.
- What software or system is affected by CVE-2023-4911?
- CVE-2023-4911 affects Red Hat Red Hat Enterprise Linux 8, Red Hat Red Hat Enterprise Linux 8, Red Hat Red Hat Enterprise Linux 8.6 Extended Update Support, Red Hat Red Hat Enterprise Linux 9, Red Hat Red Hat Enterprise Linux 9, Red Hat Red Hat Enterprise Linux 9, Red Hat Red Hat Enterprise Linux 9, Red Hat Red Hat Enterprise Linux 9.0 Extended Update Support, Red Hat Red Hat Virtualization 4 for Red Hat Enterprise Linux 8, Red Hat Red Hat Virtualization 4 for Red Hat Enterprise Linux 8, Red Hat Red Hat Virtualization 4 for Red Hat Enterprise Linux 8, Red Hat Red Hat Enterprise Linux 6, Red Hat Red Hat Enterprise Linux 7, Red Hat Red Hat Enterprise Linux 7.