Elo Ruby backend has Remote Code Execution via unescaped `#{...}` interpolation in emitted string literals and subtype-constraint labels

Summary Elo's Ruby backend emits attacker-controlled text into Ruby double-quoted strings without escaping the # character. Because # begins Ruby's interpolation sequences — #{expr}, #@ivar, #@@cvar, #$gvar — and any expression wrapped in #{...} may use backticks for shell execution, an Elo program that contains a crafted string literal or a labelled subtype constraint compiles to Ruby that evaluates attacker-chosen Ruby, and through backticks runs attacker-chosen shell commands, at runtime. The same Elo source compiled to JavaScript, Python, or SQL is benign, so the bug also breaks the cross-target portability guarantee the rest of the compiler honours. Vulnerable sinks Two sinks exist in src/compilers/ruby.ts at commit 749af7b: 1. String-literal emitter — lines 180–184. The emitter escapes backslash, double quote, and control characters, but not #. Any #{...} sequence in an Elo string literal flows straight into the emitted Ruby source. 2. Labelled subtype-constraint branch — lines 405–412. The error message passed to pfail(p, "...") is wrapped in a Ruby double-quoted string with no escape pass at all. Because the parser at src/parser.ts:1339–1348 accepts single-quoted Elo…

curl https://cve.zerocrew.in/api/cve/CVE-2026-44266