pasuwaado no tukaimawsi de huseiakusesu ga okori kanenai.

It means the reuse of passwords or using the same password over and over.

• パスワード = password
• 使い回し = repeated use, reusing the same thing for multiple purposes

So パスワードの使い回し is a noun phrase:

• password + reuse
• more naturally in English: reusing passwords

This is a very common kind of Japanese structure:

• A の B = B of A / A-related B

So here, の connects パスワード to 使い回し.

使い回し is a noun.

It comes from the verb 使い回す（つかいまわす）, which means:

• to use something again and again
• to reuse something in multiple places
• to recycle the same thing repeatedly

Examples:

• 表現を使い回す = to reuse the same expression
• パスワードを使い回す = to reuse a password

The noun 使い回し means:

• repeated use
• reuse

So:

• パスワードを使い回す = to reuse passwords
• パスワードの使い回し = password reuse

Here, で shows the cause, means, or situation that leads to something.

So パスワードの使い回しで means something like:

• through password reuse
• because of password reuse
• as a result of reusing passwords

In this sentence, it sets up the reason or condition for the danger that follows.

So the structure is roughly:

• X で Y が起こりかねない
• Because of X, Y may well happen

不正アクセス（ふせいアクセス） means unauthorized access or illegal access.

Breakdown:

• 不正 = improper, unjust, unauthorized
• アクセス = access

This is a common IT/security term in Japanese.

So 不正アクセスが means:

• unauthorized access is the thing that may happen

Because 不正アクセス is the thing that may occur.

The verb here is 起こる = to happen, to occur.
With verbs like 起こる, the event that occurs is marked with が.

So:

• 事故が起こる = an accident happens
• 問題が起こる = a problem occurs
• 不正アクセスが起こる = unauthorized access occurs

That is why が is natural here.

This is the stem form of 起こる（おこる）, meaning to happen.

In modern standard writing, you will much more often see:

• 起こりかねない

instead of:

• 起りかねない

So 起り here is essentially the same as 起こり, but with shorter okurigana. It looks a bit more formal, stiff, or old-fashioned in writing.

For most learners, it is safest to remember:

• dictionary form: 起こる
• stem form: 起こり
• common spelling in this sentence: 起こりかねない

かねない means:

• might very well ...
• there is a real danger that ...
• could easily ... in a bad way

It is usually used when the speaker thinks something undesirable may happen.

So:

• 起こりかねない = may well occur / could easily happen / there is a danger it will happen

In this sentence, it adds a warning tone:

• Unauthorized access could very well occur.
• Password reuse may lead to unauthorized access.

Good question. Both can mean may happen, but the nuance is different.

• 起こるかもしれない = it might happen

  • neutral
  • just a possibility

• 起こりかねない = it may very well happen, and that would be bad

  • more serious
  • more cautionary
  • often used for negative outcomes

So in a security warning, かねない sounds more natural because it emphasizes danger.

Japanese often uses noun-style expressions in formal or written language.

Compare:

• パスワードを使い回すと、不正アクセスが起こりかねない。

  • If you reuse passwords, unauthorized access may occur.

• パスワードの使い回しで、不正アクセスが起こりかねない。

  • Because of password reuse, unauthorized access may occur.

The version with 使い回し sounds a bit more:

• formal
• written
• explanatory
• suitable for warnings, articles, or security notices

So this sentence has a somewhat official, informative tone.

Yes, the meaning and grammar are natural, especially in written or formal contexts.

However, in modern Japanese, many people would more commonly write:

• パスワードの使い回しで、不正アクセスが起こりかねない。

with 起こり rather than 起り.

Also, in normal Japanese writing, you usually would not put spaces between words. So it would normally appear as:

• パスワードの使い回しで不正アクセスが起こりかねない。

The spaces in your version are probably just there to help learners read it.

The sentence breaks down like this:

• パスワードの使い回しで = because of password reuse
• 不正アクセスが = unauthorized access
• 起りかねない = may well occur

So the full structure is:

• [Cause/Reason] で [Event] が [may happen in a bad way]

A natural English rendering would be:

• Reusing passwords can lead to unauthorized access.
• Because of password reuse, unauthorized access may occur.
• Password reuse could result in unauthorized access.

Not always, but it often has a slightly negative or critical nuance, depending on context.

It can suggest:

• reusing something too much
• reusing something carelessly
• using the same thing where variety or caution would be better

For example:

• 同じネタの使い回し = reusing the same joke/material
• 資料の使い回し = reusing the same materials
• パスワードの使い回し = reusing the same password

In cybersecurity, it is definitely negative, because reusing passwords is risky.

You could, but it is a bit less precise.

More accurate translations would be:

• Reusing passwords can lead to unauthorized access.
• Password reuse may result in unauthorized access.
• Unauthorized access may occur because of password reuse.

Why not hacking? Because 不正アクセス specifically means unauthorized access, not necessarily all forms of hacking. Hacking is broader and less exact.

So if you want to stay close to the Japanese, unauthorized access is the best choice.