Description
The sysrq_sysctl_handler function in kernel/sysctl.c in the Linux kernel before 2.6.39 does not require the CAP_SYS_ADMIN capability to modify the dmesg_restrict value, which allows local users to bypass intended access restrictions and read the kernel ring buffer by leveraging root privileges, as demonstrated by a root user in a Linux Containers (aka LXC) environment.
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.
Red Hat
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| RHEL 6 | perf +15 | 2.6.32-220.13.1.el6 | RHSA-2012:0481 |
Advisories 1
- RHSA-2012:0481 Red Hat Security Advisory: kernel security, bug fix, and enhancement update Red Hat Security Advisories (RHSA) · Jun 28, 2026
References
- https://github.com/torvalds/linux/commit/bfdc0b497faa82a0ba2f9dddcf109231dd519fcc
- [oss-security] 20111026 Re: CVE Request -- kernel: sysctl: restrict write access to dmesg_restrict mailing-list
- http://ftp.osuosl.org/pub/linux/kernel/v2.6/ChangeLog-2.6.39
- http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git%3Ba=commit%3Bh=bfdc0b497faa82a0ba2f9dddcf109231dd519fcc