"Non-sensitizing plant extract (also known by its Latin name of Cucumis sativus). Most types of cucumber are composed of 95% water, and the other constituents primarily include ascorbic acid (vitamin C), caffeic acid (an antioxidant), fatty acids, the mineral silica, plus other trace minerals. Due to its antioxidant activity, cucumber is a welcome addition to anti-aging products.

Cucumber contains fragrant components that are not sensitizing to skin (a rarity) so it can be used to enhance the natural scent of a cosmetic product without issue." - https://www.paulaschoice.com/ingredient-dictionary/antioxidants/cucumber-extract.html

Cucumber is a nice, non-irritating plant extract that’s known for it’s soothing and emollient properties.
What research does confirm is that it contains amino acids and organic acids that’s helpful for the skin’s acid mantle. There is also an enzyme (called shikimate dehydrigenase) in the pulp that’s shown to have anti-inflammatory properties.