Know every vulnerabilitybefore it knows you.
DevGuard continuously monitors your dependencies and alerts you when CVEs like this one affect your stack — with real-time threat intelligence built for developers.
GHSA-498w-5j49-vqjg
No affected components available
Impact
For some in-circuit values, it is possible to construct two valid decomposition to bits. In addition to the canonical decomposition of a, for small values there exists a second decomposition for a+r (where r is the modulus the values are being reduced by). The second decomposition was possible due to overflowing the field where the values are defined.
Internally, the comparison methods frontend.API.Cmp and frontend.API.IsLess used binary decomposition and checked the bitwise differences. This allows a malicious prover to construct a valid proof for a statement a < b even if a > b.
The issue impacts all users using API.Cmp or API.IsLess methods. Additionally, it impacts the users using bits.ToBinary or API.ToBinary methods if full-width decomposition is requested (the default behaviour if no options are given).
The issues does not impact comparison methods in field emulation (package std/math/emulated) and dedicated comparison package (std/math/cmp).
Patches
Fix has been implemented in pull request #835 and merged in commit 59a4087261a6c73f13e80d695c17b398c3d0934f to master branch. The release v0.9.0 and onwards include the fix.
The fix added additional comparison of the decomposed bit-vector to the modulus of the in-circuit values.
Workarounds
Upgrading to version v0.9.0 should fix the issue without needing to change the calls to value comparison methods.
Alternatively, users can use the std/math/cmp gadget, which additionally allows to bound the number of bits being compared, making the comparisons more efficient if the bound on the absolute difference of the values is known.
References
- https://github.com/Consensys/gnark/pull/835
- https://github.com/zkopru-network/zkopru/issues/116
- https://github.com/iden3/circomlib/pull/48
Acknowledgement
The vulnerability was reported by Marcin Kostrzewa @ Reilabs.
The vulnerability requires local access to the device to be exploited. It is easy for an attacker to exploit this vulnerability. An attacker needs basic access or low-level privileges. No user interaction is needed for the attacker to exploit this vulnerability. The impact is confined to the system where the vulnerability exists. There is a high impact on the integrity of the data.
Exploitation attempts have been detected. Elevated vigilance and prompt remediation are advised.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
Browse More
Continuously monitor your dependencies and get alerted when vulnerabilities like this one affect your stack.
Checkout DevGuard