Meow hash 0.5/calico does not sufficiently thwart key recovery by an attacker who can query whether there's a collision in the bottom bits of the hashes of two messages, as demonstrated by an attack against a long-running web service that allows the attacker to infer collisions by measuring timing differences.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-37606
• https://news.ycombinator.com/item?id=27978878
• https://peter.website/meow-hash-cryptanalysis