Under-fire Newcastle boss Graeme Souness watched Aston Villa miss a late penalty, but nonetheless left the pitch to boos from the home faithful.
Gareth Barry sent his spot-kick high over the bar following Titus Bramble's clumsy challenge on Milan Baros.
Alan Shearer put Newcastle ahead from the spot after Liam Ridgewell's handball and also hit the bar.
But in a scrappy game, Villa equalised with 15 minutes left through McCann's low drive before Barry's aberration.
However, with the home fans disgruntled, the pressure on Souness has eased only slightly.
He responded to Wednesday's Carling Cup humiliation against Wigan by relegating Lee Bowyer and Albert Luque to the bench.
Michael Chopra, who has been in sparkling form for the reserves, got his chance up front and Amdy Faye came into midfield.
Villa boss David O'Leary also came into the match under pressure following his side's embarrassing Cup exit to Doncaster and the atmosphere was understandably tense among both sets of fans.
Those nerves quickly spread to the players.
Passed were misplaced, tackles were poorly timed, and it took 27 minutes for either side to fashion a chance, Shola Ameobi jinking past two defenders but bending his right-foot shot wide.
Five minutes later, Newcastle were ahead as the unfortunate Ridgewell inexplicably blocked Scott Parker's shot with his arm to concede a penalty for the fourth time in five games.
Shearer stepped up to move within two goals of Jackie Milburn's record of 200 goals for the Magpies.
Villa came close to equalising moments later when Hendrie sent a blistering free-kick inches wide and he thought he should have had a penalty shortly before half-time.
Baros escaped down the right and cut the ball back to the midfielder, who was booked for throwing himself to the ground under a challenge from Jean-Alain Boumsong.
Shearer put Newcastle ahead with a well-taken penalty
But while Villa undoubtedly worked hard, it was Newcastle who were marginally the more threatening going forward.
Ridgewell misjudged a Shay Given clearance and Shearer pounced, sending a sweetly-timed volley crashing onto the crossbar.
Villa responded with their first corner - after over an hour's play.
It was only half-cleared and Given was forced into an athletic save from Gareth Barry's hooked shot.
But as things began to look bleak for Villa, Barry found Hendrie in space and he pulled the ball back for McCann to drive home.
And the match almost turned completely when Bramble, so often prone to lapses in concentration, bundled over Baros.
If Souness manages to survive this period of intense speculation surrounding his future at St James' Park, he will probably have Barry's disastrous spot-kick to thank.
Newcastle boss Graeme Souness:
"I'm far happier because the team had a real go.
"If you are a paying supporter, surely you realise you cannot win every game you are involved in, but the least you can hope for from your team is to give you 100%, and we got that today.
"It's not been an enjoyable week , but it's not tough. There are far bigger things I worry about in life than football."
Aston Villa boss David O'Leary:
"We should have had all three points, but I have to praise the players and how they played.
"A few people jumped on us very quickly after the Doncaster defeat but we had won our last two league games.
"We let ourselves down but we got back to the way we were playing before the Doncaster game."
Newcastle: Given, Ramage, Boumsong, Bramble, Elliott, Solano (Bowyer 87), Faye, Parker, Shearer, Chopra (Luque 81), Ameobi.
Subs Not Used: Harper, Clark, Brittain.
Goals: Shearer 32 pen.
Aston Villa: Sorensen, Hughes, Mellberg, Ridgewell, Bouma, Hendrie, McCann, Davis (Bakke 61), Barry, Angel (Moore 62), Baros.
Subs Not Used: Samuel, Taylor, De la Cruz.
Booked: McCann, Hendrie.
Goals: McCann 75.
Ref: A Wiley (Staffordshire).