Limit XDR nesting depth when decoding contract spec/meta sections - #2668
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Pull request overview
Limits XDR decoding depth for attacker-controlled contract metadata and specs, preventing stack exhaustion.
Changes:
- Adds a depth limit of 500 to relevant XDR decoders.
- Adds tests for deeply and normally nested specifications.
leighmcculloch
approved these changes
Aug 4, 2026
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What
Decode a contract's
contractenvmetav0,contractmetav0, andcontractspecv0sections with an explicit XDR depth limit (SPEC_XDR_DEPTH_LIMIT = 500) instead ofLimits::none().Why
These sections come from attacker-authored contract WASM, and
ScSpecTypeDefis a recursive XDR type. Decoding withLimits::none()(depthu32::MAX) lets a deeply-nested type definition recurse until it exhausts the stack and aborts the process. Capping the depth turns that crash into a cleanDepthLimitExceedederror. The value 500 matchessoroban-env-host'sDEFAULT_XDR_RW_LIMITS, so any spec the network would accept still decodes, while deeper input is rejected. Tests cover both a deeply-nested spec that must be rejected and a normally-nested spec that must still decode.Known limitations
N/A