GHSA-96xm-fv9w-pf3f

Impact

Arithmetic overflow can be triggered in the Bytes::slice, Vec::slice, and Prng::gen_range (for u64) methods in the soroban-sdk in versions prior to and including 25.0.1.

Contracts that pass user-controlled or computed range bounds to Bytes::slice, Vec::slice, or Prng::gen_range may silently operate on incorrect data ranges or generate random numbers from an unintended range, potentially resulting in corrupted contract state.

Note that the best practice when using the soroban-sdk and building Soroban contracts is to always enable overflow-checks = true. The stellar contract init tool that prepares the boiler plate for a Soroban contract, as well as all examples and docs, encourage the use of configuring overflow-checks = true on release profiles so that these arithmetic operations fail rather than silently wrap. Contracts are only impacted if they use overflow-checks = false either explicitly or implicitly. It is anticipated the majority of contracts could not be impacted because the best practice encouraged by tooling is to enable overflow-checks.

Detail

When compiled with overflow-checks = false (the default for release builds), the bare arithmetic in those functions silently wraps on boundary values like u32::MAX or u64::MAX. This causes the range passed to the host to differ from the caller's intent:

Bytes::slice:

• Bytes::slice(0..=u32::MAX) — end u32::MAX + 1 wraps to 0, producing slice(0..0) returning empty instead of the full range.
• Bytes::slice((Bound::Excluded(u32::MAX), Bound::Unbounded)) — start u32::MAX + 1 wraps to 0, producing slice(0..) instead of an empty/invalid range.

Vec::slice:

• Vec::slice(0..=u32::MAX) — same as Bytes, end wraps to 0, returning empty.
• Vec::slice((Bound::Excluded(u32::MAX), Bound::Unbounded)) — same as Bytes, start wraps to 0.

Prng::gen_range:

• Prng::gen_range((Bound::Unbounded, Bound::Excluded(0))) — end 0 - 1 wraps to...