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TechQuiet 8d · day 11

Developer demonstrates undefined behavior bug in C++ that grants unintended permissions

A post showcasing a humorous but impractical example of how C++ undefined behavior can produce unintuitive security-adjacent results.

newest coverage 8d agosummary written 10d ago5 pieces33 likes & upvotes17 comments Hacker NewsMastodonNewswiresLobsters

What to know

  • A developer published a humorous example of C++ undefined behavior causing a program to appear to grant unintended permissions under specific compiler and code conditions.
  • The author emphasizes this is not a practical security risk, as the bug depends on precise circumstances (string length matching, inlining, optimization flags) that standard refactoring eliminates.
  • The post uses Halloween-themed language as a framing device while explaining underlying technical concepts about undefined behavior in C++.

nablags Blog author

How it unfolded 1 development · click the chart to see its coverage articlesposts

Peak 3 pieces in 3h at Oct 31, 5 PM; 5 pieces over 11 days (1 article · 4 posts) Oct 31, 5 PM — 3 pieces · 1 article · 2 posts — Hacker News 1, Newswires 1, Mastodon 1Oct 31, 8 PM — quietOct 31, 11 PM — quietNov 1, 1 AM — quietNov 1, 4 AM — quietNov 1, 7 AM — quietNov 1, 10 AM — 1 piece · 1 post — Lobsters 1Nov 1, 1 PM — quietNov 1, 4 PM — quietNov 1, 7 PM — quietNov 1, 10 PM — quietNov 2, 1 AM — quietNov 2, 4 AM — quietNov 2, 7 AM — quietNov 2, 10 AM — quietNov 2, 1 PM — quietNov 2, 4 PM — quietNov 2, 7 PM — quietNov 2, 10 PM — quietNov 3, 1 AM — quietNov 3, 4 AM — quietNov 3, 7 AM — quietNov 3, 10 AM — quietNov 3, 1 PM — 1 piece · 1 post — Hacker News 1Nov 3, 4 PM — quietNov 3, 7 PM — quietNov 3, 10 PM — quietNov 4, 1 AM — quietNov 4, 4 AM — quietNov 4, 7 AM — quietNov 4, 10 AM — quietNov 4, 1 PM — quietNov 4, 4 PM — quietNov 4, 7 PM — quietNov 4, 10 PM — quietNov 5, 1 AM — quietNov 5, 4 AM — quietNov 5, 7 AM — quietNov 5, 10 AM — quietNov 5, 1 PM — quietNov 5, 4 PM — quietNov 5, 7 PM — quietNov 5, 10 PM — quietNov 6, 1 AM — quietNov 6, 4 AM — quietNov 6, 7 AM — quietNov 6, 10 AM — quietNov 6, 1 PM — quietNov 6, 4 PM — quietNov 6, 7 PM — quietNov 6, 10 PM — quietNov 7, 1 AM — quietNov 7, 4 AM — quietNov 7, 7 AM — quietNov 7, 10 AM — quietNov 7, 1 PM — quietNov 7, 4 PM — quietNov 7, 7 PM — quietNov 7, 10 PM — quietNov 8, 1 AM — quietNov 8, 4 AM — quietNov 8, 7 AM — quietNov 8, 10 AM — quietNov 8, 1 PM — quietNov 8, 4 PM — quietNov 8, 7 PM — quietNov 8, 10 PM — quietNov 9, 1 AM — quietNov 9, 4 AM — quietNov 9, 7 AM — quietNov 9, 10 AM — quietNov 9, 1 PM — quietNov 9, 4 PM — quietNov 9, 7 PM — quietNov 9, 10 PM — quietYesterday, 1 AM — quietYesterday, 4 AM — quietYesterday, 7 AM — quietYesterday, 10 AM — quietYesterday, 1 PM — quietYesterday, 4 PM — quietYesterday, 7 PM — quietYesterday, 10 PM — quietToday, 1 AM — quietToday, 4 AM — quietToday, 7 AM — quietToday, 10 AM — quietToday, 1 PM — quietToday, 4 PM — quiet 1
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  1. 1

    Author frames bug as illustrative but practically unlikely to exploit

    The post explains the phenomenon as undefined behavior and notes the bug is not a practical security concern. The author argues it depends on specific conditions (matching string lengths, inlining, lack of refactoring) that would be eliminated by standard coding practices.

    “Even though this is a funny example, I doubt a bug like this will surface in the wild (nor be easily exploited) as this behavior is incredibly hard to reproduce.”
    — nablags
    • hkrn@mstdn.social

      Spooky C++ L: https://www. nablag.com/spooky_cpp C: https:// news.ycombinator.com/item?id=5 0320513 posted on 2026.10.31 at 17:40:18 (c=1, p=6)

      hkrn@mstdn.socialMastodon11d agoview on Mastodon ↗
  2. background

    Developer publishes "Spooky C++" post on undefined behavior bug — A blog post titled "Spooky C++" was published documenting a C++ program exhibiting undefined behavior. The post humorously describes conditions under which a permission-granting bug appears: compiling with -O2 optimization after -O0, dependent on string length matching and inline parameter passing.