The vulnerability in dash's printf builtin arises because it reserves only four bytes before converting Unicode \u or \U escapes, whereas the multi-byte token can require five or six bytes. This causes a local user who can supply such escape sequences to write one or two bytes beyond the reserved buffer, resulting in an out-of-bounds heap memory write. The flaw affects environments where dash is deliberately installed and used, as Red Hat Enterprise Linux 6 uses bash as the default system shell. The issue is rated moderate severity due to the need for local access and crafted input. The advisory notes no practical runtime mitigation other than avoiding untrusted input to dash printf/echo %b or dash -c positional arguments. The fix is to increase the buffer reservation from four to eight bytes at the printf call sites. No official patch or fixed version is explicitly stated in the advisory.

The vulnerability allows a local user to cause out-of-bounds heap memory writes by supplying crafted Unicode escape sequences to dash's printf or echo %b builtins. This can lead to memory corruption, potentially causing unexpected behavior or denial of service via crashes. However, under standard operating conditions, it does not result in direct privilege escalation. The exposure is limited to systems where dash is installed and used on untrusted input, which is not the default in Red Hat Enterprise Linux 6.

No practical runtime mitigation is available in the shipped build. Users should avoid passing untrusted data into dash printf, echo %b, or dash -c as a positional argument. The advisory indicates the fix requires increasing the buffer reservation size in the source code. Users should monitor Red Hat advisories for an official patch release and apply it once available.