Description
An issue was discovered in the Linux kernel 5.4 and 5.5 through 5.5.6 on the AArch64 architecture. It ignores the top byte in the address passed to the brk system call, potentially moving the memory break downwards when the application expects it to move upwards, aka CID-dcde237319e6. This has been observed to cause heap corruption with the GNU C Library malloc implementation.
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 | 5.5.13-1 | — |
| Debian 13 | linux | 5.5.13-1 | — |
| Debian 12 | linux | 5.5.13-1 | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 20.04 LTS | linux-raspi2 | No fix yet | — |
| Ubuntu 18.04 LTS | linux-gcp-edge +2 | No fix yet | — |
| Ubuntu 16.04 LTS | linux-hwe-edge | No fix yet | — |
Oracle Linux
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Oracle Linux 7 | kernel-uek +4 | 5.4.17-2011.2.2.el8uek | ELSA-2020-5691 |
| Oracle Linux 7 | perf +3 | 5.4.17-2011.2.2.el7uek | ELSA-2020-5691 |
Advisories 1
- ELSA-2020-5691 Important: Unbreakable Enterprise kernel security update (Oracle Linux 7) Oracle Linux Security Advisories (ELSA) · May 18, 2020
References
- https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=dcde237319e626d1ec3c9d8b7613032f0fd4663a
- https://bugzilla.redhat.com/show_bug.cgi?id=1797052
- [oss-security] 20200225 CVE-2020-9391: Ignoring the top byte of addresses in brk causes heap corruption (AArch64) mailing-list
- FEDORA-2020-3cd64d683c vendor-advisory
- https://security.netapp.com/advisory/ntap-20200313-0003/