In the Linux kernel, the following vulnerability has been resolved:
exec: Force single empty string when argv is empty
Quoting[1] Ariadne Conill:
"In several other operating systems, it is a hard requirement that the second argument to execve(2) be the name of a program, thus prohibiting a scenario where argc < 1. POSIX 2017 also recommends this behaviour, but it is not an explicit requirement[2]:
The argument arg0 should point to a filename string that is associated with the process being started by one of the exec functions. ... Interestingly, Michael Kerrisk opened an issue about this in 2008[3], but there was no consensus to support fixing this issue then. Hopefully now that CVE-2021-4034 shows practical exploitative use[4] of this bug in a shellcode, we can reconsider.
This issue is being tracked in the KSPP issue tracker[5]."
While the initial code searches[6][7] turned up what appeared to be mostly corner case tests, trying to that just reject argv == NULL (or an immediately terminated pointer list) quickly started tripping[8] existing userspace programs.
The next best approach is forcing a single empty string into argv and adjusting argc to match. The number of programs depending on argc == 0 seems a smaller set than those calling execve with a NULL argv.
Account for the additional stack space in bprm_stack_limits(). Inject an empty string when argc == 0 (and set argc = 1). Warn about the case so userspace has some notice about the change:
process './argc0' launched './argc0' with NULL argv: empty string added
Additionally WARN() and reject NULL argv usage for kernel threads.
[1] https://lore.kernel.org/lkml/[email protected]/ [2] https://pubs.opengroup.org/onlinepubs/9699919799/functions/exec.html [3] https://bugzilla.kernel.org/show_bug.cgi?id=8408 [4] https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt [5] https://github.com/KSPP/linux/issues/176 [6] https://codesearch.debian.net/search?q=execve%5C+*%5C%28%5B%5E%2C%5D%2B%2C+*NULL&literal=0 [7] https://codesearch.debian.net/search?q=execlp%3F%5Cs*%5C%28%5B%5E%2C%5D%2B%2C%5Cs*NULL&literal=0 [8] https://lore.kernel.org/lkml/20220131144352.GE16385@xsang-OptiPlex-9020/
CVSS Details
- CVSS 3.1 Base Score: 7.8
- CVSS 3.1 Vector: (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
Covered by Rapid7
| Product | Vendor Advisory | Solution File | Added | Published |
|---|---|---|---|---|
| Amazon Linux Ami 2 | — | Upgrade kernel-livepatch-4.14.285-215.501Upgrade bpftoolUpgrade python-perfUpgrade perfUpgrade kernel-debuginfo-common-aarch64Upgrade kernel-toolsUpgrade kernel-livepatch-5.10.112-108.499Upgrade kernel-tools-develUpgrade perf-debuginfoUpgrade kernel-debuginfo-common-x86_64Upgrade kernel-tools-debuginfoUpgrade kernel-debuginfoUpgrade kernel-develUpgrade kernel-headersUpgrade python-perf-debuginfoUpgrade bpftool-debuginfoUpgrade kernel | May 21, 2025 | Feb 26, 2025 |
| Debian | — | Upgrade linux | Feb 27, 2025 | Feb 27, 2025 |
| Huawei Euleros 2_0_sp10 | — | Upgrade python3-perfUpgrade kernelUpgrade kernel-abi-stablelistsUpgrade kernel-toolsUpgrade kernel-tools-libs | May 13, 2025 | Feb 26, 2025 |
| Huawei Euleros 2_0_sp13 | — | Upgrade bpftoolUpgrade kernelUpgrade python3-perfUpgrade kernel-toolsUpgrade kernel-tools-libsUpgrade kernel-abi-stablelists | Jul 1, 2025 | Feb 26, 2025 |
| Redhat_linux | — | No solution exists | Jul 9, 2025 | Feb 26, 2025 |
| Ubuntu | — | Upgrade linux-fipsUpgrade linux-lowlatencyUpgrade linux-aws-hweUpgrade linux-oracle-5.4Upgrade linux-gkeUpgrade linux-intel-iotgUpgrade linuxUpgrade linux-lowlatency-hwe-5.15Upgrade linux-realtimeUpgrade linux-ibm-5.4Upgrade linux-aws-5.4Upgrade linux-raspiUpgrade linux-gcp-fipsUpgrade linux-oracleUpgrade linux-gcpUpgrade linux-kvmUpgrade linux-azureUpgrade linux-raspi-5.4Upgrade linux-bluefieldUpgrade linux-intel-iotg-5.15Upgrade linux-aws-fipsUpgrade linux-gcp-5.4Upgrade linux-azure-5.15Upgrade linux-azure-fipsUpgrade linux-azure-5.4Upgrade linux-hwe-5.15Upgrade linux-hwe-5.4Upgrade linux-hweUpgrade linux-azure-4.15Upgrade linux-gcp-4.15Upgrade linux-iotUpgrade linux-ibmUpgrade linux-aws | Mar 3, 2025 | Feb 26, 2025 |
| Vmware Photon_os | — | Use 'tdnf update' to upgrade all packages to the latest version. | May 27, 2026 | Feb 26, 2025 |
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