CVE-2019-19039

Published: 21 November 2019

** DISPUTED ** __btrfs_free_extent in fs/btrfs/extent-tree.c in the Linux kernel through 5.3.12 calls btrfs_print_leaf in a certain ENOENT case, which allows local users to obtain potentially sensitive information about register values via the dmesg program. NOTE: The BTRFS development team disputes this issues as not being a vulnerability because “1) The kernel provide facilities to restrict access to dmesg - dmesg_restrict=1 sysctl option. So it's really up to the system administrator to judge whether dmesg access shall be disallowed or not. 2) WARN/WARN_ON are widely used macros in the linux kernel. If this CVE is considered valid this would mean there are literally thousands CVE lurking in the kernel - something which clearly is not the case.”

From the Ubuntu Security Team

It was discovered that the btrfs file system in the Linux kernel in some error conditions could report register information to the dmesg buffer. A local attacker could possibly use this to expose sensitive information.

Notes

Exploiting this vulnerability requires a crafted filesystem image to
be mounted

Mitigation

| sudo sysctl kernel.dmesg_restrict=1

Status

Severity score breakdown

References

• https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2019-19039
• https://github.com/bobfuzzer/CVE/tree/master/CVE-2019-19039
• https://ubuntu.com/security/notices/USN-4414-1
• NVD
• Launchpad
• Debian

Bugs

• https://bugzilla.suse.com/show_bug.cgi?id=1157719