The resolveImplicitLevels function in common/ubidi.c in the Unicode Bidirectional Algorithm implementation in ICU4C in International Components for Unicode (ICU) before 55.1 does not properly track directionally isolated pieces of text, which allows remote attackers to cause a denial of service (heap-based buffer overflow) or possibly execute arbitrary code via crafted text.
Improper Restriction of Operations within the Bounds of a Memory Buffer The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary.