CVE-2026-10512 — X25519 x86_64 assembly final reduction leaves non-canonical field element
The X25519 x86_64 assembly implementation fails to clear the most significant bit during the final modular reduction, so the computed result may not be fully reduced modulo the …
Published: 2026-06-25 · CVSS: 2.3 · CVSS 4.0
The X25519 x86_64 assembly implementation fails to clear the most significant bit during the final modular reduction, so the computed result may not be fully reduced modulo the field prime 2^255 - 19. This can leave the field element in a non-canonical form, producing an incorrect result from the scalar multiplication and potentially a wrong shared secret. The final carry-propagation chains in the x64 and AVX2 reduction routines could overflow into the top bit, and the high limb was not masked afterward, so the 255-bit field element was left non-canonical.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7