** Shares of Cognizant Technology CTSH.O up 4.5% at $86.99, bucking broad tumble in equities on Mon, after report of activist investor's stake boost

** Stock tracking biggest one-day pct gain since Nov 6

** Mantle Ridge has built >$1 bln stake in the consultancy firm, saying its shares are undervalued, the WSJ reported late Fri

** It began buying CTSH shares H2 2022 when stock was trading in range of high $50s to low $60s, according to the report

** Co told Reuters it and its board has been "constructively engaging" with Mantle Ridge since mid-2024, and the activist investor has expressed support for management and board "on multiple occasions"

** Guggenheim said in research note after its weekend discussions with Mantle Ridge, it understands Mantle Ridge's belief that CTSH's "motivated and experienced management team can continue to demonstrate progress around growth and margin expansion"

** Guggenheim, which rates CTSH 'neutral', pointed to the shares trading at 15.5x its CY26 EPS estimates, which is below diversified peer group avg of 19.9x

** Avg rating among 27 brokerages covering CTSH is "hold" with $88 median PT, per LSEG

** With moves on the session, stock up ~13% YTD vs S&P 500 Tech sector's .SPLRCT 11% drop and the Nasdaq's .IXIC 9% decline

(Lance Tupper is a Reuters market analyst. The views expressed are his own)

((lance.tupper@tr.com 1-646-279-6380))