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. 

References

• https://nvd.nist.gov/vuln/detail/CVE-2023-1999
• https://chromium.googlesource.com/webm/libwebp
• https://security.gentoo.org/glsa/202309-05