CVE-2020-10773

A stack information leak flaw was found in s390/s390x in the Linux kernel’s memory manager functionality, where it incorrectly writes to the /proc/sys/vm/cmm_timeout file. This flaw allows a local user to see the kernel data.

Weakness

The product does not properly handle null bytes or NUL characters when passing data between different representations or components.

Affected Software

Extended Description

A null byte (NUL character) can have different meanings across representations or languages. For example, it is a string terminator in standard C libraries, but Perl and PHP strings do not treat it as a terminator. When two representations are crossed - such as when Perl or PHP invokes underlying C functionality - this can produce an interaction error with unexpected results. Similar issues have been reported for ASP. Other interpreters written in C might also be affected. The poison null byte is frequently useful in path traversal attacks by terminating hard-coded extensions that are added to a filename. It can play a role in regular expression processing in PHP.

Potential Mitigations

References

• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2020-10773
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b8e51a6a9db94bc1fb18ae831b3dab106b5a4b5f
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2020-10773
• https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=b8e51a6a9db94bc1fb18ae831b3dab106b5a4b5f