RUSTSEC-2026-0212 Potentially Incorrect Output of Constant-Time Swap/Select on Aarch64
Incorrect constant-time swap/select results on Aarch64 due to register bit leakage, potentially compromising cryptographic security.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Not stated
- Victim action needed
- Not needed
- Fix
- Available
What is RUSTSEC-2026-0212?
RUSTSEC-2026-0212 is a vulnerability in libcrux-secrets, published on 26 May 2026.
Official description
The implementation of constant-time swap and select on aarch64
platforms used a cmp instruction in inline assembly to check whether
an 8-bit wide selector was 0. The cmp instruction works on 32-bit
registers, which included the unspecified high 24 bits of the cmp operand.
Depending on the execution environment the cmp
could thus potentially return an incorrect result because its
operand's high bits in the inline assembly were set when Rust expected them to be unset.
This could lead to incorrect results for the constant-time swap and select
operations built from this comparison.
Impact
In certain circumstances the swap and select instructions on aarch64 platforms returned incorrect results.
Mitigation
Starting from version 0.0.6, the selector is compared using a tst
instruction with a mask, which only compares the first 8 bits of the
selector.
Which versions are affected by RUSTSEC-2026-0212?
1 open source package ship an affected version, including libcrux-secrets.
| Package | Affected | Fixed in |
|---|---|---|
libcrux-secrets crates.io | From 0.0.0-0 | 0.0.6 |
How do I fix RUSTSEC-2026-0212?
Upgrade libcrux-secrets to 0.0.6 or later.
Is RUSTSEC-2026-0212 being exploited?
There is no known exploitation of RUSTSEC-2026-0212 in the wild and no public exploit code.