Description
A flaw was found in the way the dumpable flag setting was handled when certain SUID binaries executed its descendants. The prerequisite is a SUID binary that sets real UID equal to effective UID, and real GID equal to effective GID. The descendant will then have a dumpable value set to 1. As a result, if the descendant process crashes and core_pattern is set to a relative value, its core dump is stored in the current directory with uid:gid permissions. An unprivileged local user with eligible root SUID binary could use this flaw to place core dumps into root-owned directories, potentially resulting in escalation of privileges.
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| — | kernel | Not Known | — |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | linux | No fix yet | — |
| Debian 13 | linux | No fix yet | — |
| Debian 12 | linux | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Nvidia-BlueField 24.04 LTS | linux-bluefield | No fix yet | — |
| Ubuntu Nvidia-BlueField 22.04 LTS | linux-bluefield | No fix yet | — |
| Ubuntu 26.10 | linux +8 | No fix yet | — |
| Ubuntu 26.04 LTS | linux +14 | No fix yet | — |
| Ubuntu 25.10 | linux +8 | No fix yet | — |
Show 20 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 24.04 LTS | linux +53 | No fix yet | — |
| Ubuntu 22.04 LTS | linux +59 | No fix yet | — |
| Ubuntu 20.04 LTS | linux-gke +28 | No fix yet | — |
| Ubuntu 18.04 LTS | linux-gcp +14 | No fix yet | — |
| Ubuntu 16.04 LTS | linux-hwe-edge | No fix yet | — |
| Ubuntu Pro Realtime 24.04 LTS | linux-realtime +3 | No fix yet | — |
| Ubuntu Pro Realtime 22.04 LTS | linux-realtime +2 | No fix yet | — |
| Ubuntu Pro FIPS 20.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS 18.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS 16.04 LTS | linux-fips | No fix yet | — |
| Ubuntu Pro FIPS-updates 24.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS-updates 22.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS-updates 20.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS-updates 18.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro FIPS-updates 16.04 LTS | linux-fips | No fix yet | — |
| Ubuntu Pro FIPS-preview 22.04 LTS | linux-fips +3 | No fix yet | — |
| Ubuntu Pro 20.04 LTS | linux +21 | No fix yet | — |
| Ubuntu Pro 18.04 LTS | linux +12 | No fix yet | — |
| Ubuntu Pro 16.04 LTS | linux +7 | No fix yet | — |
| Ubuntu Pro 14.04 LTS | linux +3 | No fix yet | — |
Public exploits
Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.
GitHub 1 repository
-
walac/cve-2021-3864 ★ 0 · Mar 31, 2022
Test for cve-2021-3864
Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.
Advisories 1
- WID-SEC-2022-1257 Linux Kernel: Mehrere Schwachstellen BSI CERT-Bund (WID) · Jun 24, 2024
References
- https://www.openwall.com/lists/oss-security/2021/10/20/2
- https://bugzilla.redhat.com/show_bug.cgi?id=2015046
- https://access.redhat.com/security/cve/CVE-2021-3864
- https://lore.kernel.org/all/20211221021744.864115-1-longman%40redhat.com/
- https://lore.kernel.org/lkml/20211228170910.623156-1-wander%40redhat.com/
- https://lore.kernel.org/all/20211226150310.GA992%401wt.eu/
- https://security-tracker.debian.org/tracker/CVE-2021-3864