There exists a use after free/double free in libwebp. An attacker can use the ApplyFiltersAndEncode() function and loop through to free best.bw and assign best = trial pointer. The second loop will then return 0 because of an Out of memory error in VP8 encoder, the pointer is still assigned to trial and the AddressSanitizer will attempt a double free.
Exploitability
AV:NAC:HPR:LUI:NScope
S:UImpact
C:HI:NA:N5.3/CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:NMemory Safety