RUSTSEC-2026-0220None▾ SunlitUint shift operations: incorrect overflow flags and truncated shift amounts
▾ Sunlit zone — Low / medium · no exploitation signal
impact 2.8 · likelihood 0 · exploitation 0
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Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via OSV
Last analysed / modified upstream
Uint::overflowing_shl/overflowing_shr returned false-negative overflow
flags. overflowing_shl missed bits shifted above BITS but within the top
limb (non-limb-aligned widths such as U160), and limbs wholly discarded by
shifts >= 64; overflowing_shr missed wholly discarded low limbs. Shifted
values were correct; only the flag was wrong.
The wrong flag propagates: checked_shl/checked_shr return Some instead
of None, strict_* fail to panic, and saturating_* return a wrapped
value instead of saturating. The incorrect checked_shl result causes
to_base_be (and string formatting) to loop forever on no-alloc builds for
non-limb-aligned widths — a denial of service if formatting is reachable
from untrusted input.
Separately, wrapping_shl/wrapping_shr on 64/128/256-bit types truncated
the shift amount modulo 2^32, so shifts >= 2^32 returned an incorrectly
wrapped value instead of zero; on 32-bit targets the generic path also
truncated 64-bit shift amounts.
Callers using checked or saturating shift semantics on untrusted shift amounts may compute incorrect results.
ruint >= 0.0.0-0, < 1.20.0Upgrade to a patched release:
ruint 1.20.0