Yes. In Palworld v1.0.3, Gumoss can get Ferocious through currently verified methods: it is in the standard random pool. Ferocious is in the standard random passive pool in v1.0.3, so it can appear on a caught or bred Gumoss and be inherited from parents that have it. The facts behind this answer are graded B and come from 2 registered sources.
Reason
Attack +20%
Rank
3
Random pool
Yes
Other Pals
299
Gumoss breeding recipes
1
Fixed passives on Gumoss
0
Custom slots available
4
Verified evidence claims behind this verdict
1
Gumoss parent pairs with a direct source of Ferocious
1 of 1
Ferocious breeding route for Gumoss: 1 of 1 parent pair include a direct source (Gumoss).
Why
Ferocious is in the standard random passive pool in v1.0.3, so it can appear on a caught or bred Gumoss and be inherited from parents that have it.
How Ferocious can be acquired on Gumoss in v1.0.3
Current method
Available for Gumoss?
Note
Fixed / innate
No
Gumoss is born with no fixed passive.
Random pool (catch or hatch)
Yes
Ferocious is in the standard random pool, so it can appear on a caught or hatched Gumoss.
Implant (Surgery Table)
No
Ferocious: no verified item method grants it here.
Breeding inheritance
Yes
Gumoss can inherit Ferocious along a verified breeding chain, under the standard passive-inheritance rule this dataset has not independently sourced.
Verdict per requested component on Gumoss in Palworld v1.0.3
Ferocious is in the standard random passive pool in v1.0.3, so it can appear on a caught or bred Gumoss and be inherited from parents that have it.
B B · 1 source
How it reaches this Pal
Ferocious is in the standard random pool, so it can appear on a caught or hatched Gumoss.
299 Pals obtain Ferocious directly in v1.0.3 (Demon Eye, Depresso, Digtoise, Dinossom and Dinossom Lux).
Gumoss breeds only from two Gumoss parents in v1.0.3, so no other species can bring Ferocious into its line.
5 of 299 shown
What you can do now
Ferocious is in the standard random pool, so it can appear on a caught or hatched Gumoss.
Alternative: Gumoss can inherit Ferocious along a verified breeding chain, under the standard passive-inheritance rule this dataset has not independently sourced.