Shares closed regular trading up $4.56, or 21 percent, to $25.88.
Prudential Securities analyst John McPeake said BMC Software's positive pre-announcement Wednesday likely signals a bottom for Computer Associates and the rest of the mainframe software sector.
BMC, which McPeake upgraded from a "hold" rating to a "strong buy," shot up 41 percent.
"With CA's stock trading near five-year lows, at the current valuation we think downside risk is limited," he said in a research note.
Computer Associates topped analysts' reduced estimates last quarter, earning $321 million, or 54 cents a share, on sales of $1.68 billion.
Analysts polled by First Call expect it to earn 40 cents a share in its third quarter on sales of around $1.4 billion.
The stock moved as high as $79.44 in January before falling to a 52-week low of $18.13 in December.
Eleven of the 20 analysts tracking the stock maintain either a "buy" or "strong buy" recommendation.