Unpatched extfs vulnerabilities are exploitable through suid-mode Apptainer

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Apptainer is an open source container platform for Linux. There is an ext4 use-after-free flaw that is exploitable through versions of Apptainer < 1.1.0 and installations that include apptainer-suid < 1.1.8 on older operating systems where that CVE has not been patched. That includes Red Hat Enterprise Linux 7, Debian 10 buster (unless the linux-5.10 package is installed), Ubuntu 18.04 bionic and Ubuntu 20.04 focal. Use-after-free flaws in the kernel can be used to attack the kernel for denial of service and potentially for privilege escalation. Apptainer 1.1.8 includes a patch that by default disables mounting of extfs filesystem types in setuid-root mode, while continuing to allow mounting of extfs filesystems in non-setuid "rootless" mode using fuse2fs. Some workarounds are possible. Either do not install apptainer-suid (for versions 1.1.0 through 1.1.7) or set `allow setuid = no` in apptainer.conf. This requires having unprivileged user namespaces enabled and except for apptainer 1.1.x versions will disallow mounting of sif files, extfs files, and squashfs files in addition to other, less significant impacts. (Encrypted sif files are also not supported unprivileged in apptainer 1.1.x.). Alternatively, use the `limit containers` options in apptainer.conf/singularity.conf to limit sif files to trusted users, groups, and/or paths, and set `allow container extfs = no` to disallow mounting of extfs overlay files. The latter option by itself does not disallow mounting of extfs overlay partitions inside SIF files, so that's why the former options are also needed.

Source published

25 Apr 2023 00:00:00 UTC

Source modified

5 Mar 2025 19:03:47 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 7.1 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Apptainer is an open source container platform for Linux. There is an ext4 use-after-free flaw that is exploitable through versions of Apptainer < 1.1.0 and installations that include apptainer-suid < 1.1.8 on older operating systems where that CVE has not been patched. That includes Red Hat Enterprise Linux 7, Debian 10 buster (unless the linux-5.10 package is installed), Ubuntu 18.04 bionic and Ubuntu 20.04 focal. Use-after-free flaws in the kernel can be used to attack the kernel for denial of service and potentially for privilege escalation. Apptainer 1.1.8 includes a patch that by default disables mounting of extfs filesystem types in setuid-root mode, while continuing to allow mounting of extfs filesystems in non-setuid "rootless" mode using fuse2fs. Some workarounds are possible. Either do not install apptainer-suid (for versions 1.1.0 through 1.1.7) or set `allow setuid = no` in apptainer.conf. This requires having unprivileged user namespaces enabled and except for apptainer 1.1.x versions will disallow mounting of sif files, extfs files, and squashfs files in addition to other, less significant impacts. (Encrypted sif files are also not supported unprivileged in apptainer 1.1.x.). Alternatively, use the `limit containers` options in apptainer.conf/singularity.conf to limit sif files to trusted users, groups, and/or paths, and set `allow container extfs = no` to disallow mounting of extfs overlay files. The latter option by itself does not disallow mounting of extfs overlay partitions inside SIF files, so that's why the former options are also needed.

Source published

Apr 25, 2023, 12:00:00 AM (timezone not stated)

Source modified

Mar 5, 2025, 7:03:47 PM (timezone not stated)

Observed here

24 Oct 2026 22:25:44 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 7.1 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Apptainer is an open source container platform for Linux. There is an ext4 use-after-free flaw that is exploitable through versions of Apptainer < 1.1.0 and installations that include apptainer-suid < 1.1.8 on older operating systems where that CVE has not been patched. That includes Red Hat Enterprise Linux 7, Debian 10 buster (unless the linux-5.10 package is installed), Ubuntu 18.04 bionic and Ubuntu 20.04 focal. Use-after-free flaws in the kernel can be used to attack the kernel for denial of service and potentially for privilege escalation. Apptainer 1.1.8 includes a patch that by default disables mounting of extfs filesystem types in setuid-root mode, while continuing to allow mounting of extfs filesystems in non-setuid "rootless" mode using fuse2fs. Some workarounds are possible. Either do not install apptainer-suid (for versions 1.1.0 through 1.1.7) or set `allow setuid = no` in apptainer.conf. This requires having unprivileged user namespaces enabled and except for apptainer 1.1.x versions will disallow mounting of sif files, extfs files, and squashfs files in addition to other, less significant impacts. (Encrypted sif files are also not supported unprivileged in apptainer 1.1.x.). Alternatively, use the `limit containers` options in apptainer.conf/singularity.conf to limit sif files to trusted users, groups, and/or paths, and set `allow container extfs = no` to disallow mounting of extfs overlay files. The latter option by itself does not disallow mounting of extfs overlay partitions inside SIF files, so that's why the former options are also needed.

Source published

25 Apr 2023 21:15:10 UTC

Source modified

23 Oct 2026 23:10:00 UTC

Observed here

24 Oct 2026 22:17:10 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.1 CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

CVSS 3.1 · [email protected] · Primary · 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

### Impact There is an ext4 use-after-free flaw described in CVE-2022-1184 that is exploitable through versions of Apptainer < 1.1.0 and installations that include apptainer-suid < 1.1.8 on older operating systems where that CVE has not been patched. That includes Red Hat Enterprise Linux 7, Debian 10 buster (unless the linux-5.10 package is installed), Ubuntu 18.04 bionic and Ubuntu 20.04 focal. Use-after-free flaws in the kernel can be used to attack the kernel for denial of service and potentially for privilege escalation. ### Background Historically there have been many CVEs published for extfs and a smaller number for squashfs, including serious use-after-free and buffer overrun vulnerabilities, that are scored as "Moderate" or "Low" impact only because unprivileged users were assumed to not have write access to the raw data. Because of those ratings, vendors treat such CVEs as low urgency and either delay a patch until their next major release or never patch older but still supported operating systems at all. Many Linux distributions automatically mount user-writable USB-drive volumes, but those are considered low risk because they require physical access to the machine. However, since setuid-root installations of Apptainer by default allow all users to mount any extfs (specifically, ext3, which is implemented by the ext4 driver) and squashfs filesystem using kernel drivers even though the users have write access to the raw data, the setuid-root installations raise the severity of such unpatched CVEs. CVE-2022-1184 is currently such an unpatched CVE, at least on the above listed operating systems. The descriptions from the operating system vendors about the CVE (referenced below) are incomplete, saying only that it allows a local attacker with user privilege to cause a denial of service. Normally users would not be able to cause it because they cannot modify the filesystem image, and normally vulnerabilities that involve kernel memory corruption by unprivileged users are considered high severity even when there is not yet a known privilege escalation because someone with sufficient kernel knowledge can usually turn such a corruption into a privilege escalation. Red Hat did not list RHEL7 as vulnerable, but they also did not list it as unaffected, and testing confirmed that a filesystem image could be corrupted to get past the check inserted into the filesystem driver to fix the vulnerability (patches linked below). All published squashfs CVEs have been patched in currently supported major operating systems. ### Patches Apptainer 1.1.8 includes a patch that by default disables mounting of extfs filesystem types in setuid-root mode, while continuing to allow mounting of extfs filesystems in non-setuid "rootless" mode using fuse2fs. ### Workarounds These workarounds are possible: 1. Either do not install apptainer-suid (for versions 1.1.0 through 1.1.7) or set `allow setuid = no` in apptainer.conf. This requires having unprivileged user namespaces enabled and except for apptainer 1.1.x versions will disallow mounting of sif files, extfs files, and squashfs files in addition to other, less significant impacts. (Encrypted sif files are also not supported unprivileged in apptainer 1.1.x.) 2. Alternatively, use the `limit containers` options in apptainer.conf/singularity.conf to limit sif files to trusted users, groups, and/or paths. (The option `allow container extfs = no` disallows mounting extfs overlay files but does not disallow mounting of extfs overlay partitions inside SIF files, so it does not help work around the problem.) ### References https://nvd.nist.gov/vuln/detail/CVE-2022-1184 https://access.redhat.com/security/cve/cve-2022-1184 https://security-tracker.debian.org/tracker/CVE-2022-1184 https://ubuntu.com/security/CVE-2022-1184 Kernel patches for CVE-2022-1184: https://github.com/torvalds/linux/commit/65f8ea4cd57dbd46ea13b41dc8bac03176b04233 https://github.com/torvalds/linux/commit/61a1d87a324ad5e3ed27c6699dfc93218fcf3201 ------ ## Addendum 30 May 2023 New information has become available: many ext4 filesytem vulnerabilities similar to the one in CVE-2022-1184 continue to be found, and most of them do not ever have a CVE assigned. The way to locate them is to search for "syzbot" in linux kernel commit messages under fs/ext4. "syzbot" is a public automated system for finding kernel bugs. Especially when syzbot reports are labeled "KASAN" (Kernel Address Sanitizer) and especially if they involve memory corruption including "use after free", "out of bounds", or "user-memory-access", they are vulnerabilities that can potentially be turned into privilege escalation when an unprivileged user has write access to the underlying data. In particular there are two such commits from this month, May 2023, referenced below. They both have commit messages describing a situation of write access to the underlying data while the kernel has that data mounted as a filesystem. These commits have been backported to currently maintained kernel lines in versions 4.19.293 and 5.4.243, but since they are considered moderate severity, most common OS distributions do not include them immediately. For example since RHEL9.2 was recently announced, they are not likely to be available in RHEL9 until 9.3 is released in about another 6 months. Therefore if system administrators want to be protected against these vulnerabilities while still allowing ext4 filesystem mounts through setuid-root apptainer, they should watch for these types of commits and whenever such commits are released the administrators should update to the latest currently maintained kernel version (bypassing their OS vendor's distribution) and reboot. https://github.com/torvalds/linux/commit/2220eaf90992c11d888fe771055d4de3303 https://github.com/torvalds/linux/commit/4f04351888a83e595571de672e0a4a8b74f https://lwn.net/Articles/932137/ https://lwn.net/Articles/932136/

Source published

25 Apr 2023 19:48:35 UTC

Source modified

20 Aug 2024 20:58:34 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

Publisher rating · HIGH

Unpatched extfs vulnerabilities are exploitable through suid-mode Apptainer in github.com/apptainer/apptainer

Source published

20 Aug 2024 20:29:19 UTC

Source modified

3 Mar 2026 04:53:40 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.