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Fix: clamp excessive entity velocities to [-4,4] to prevent plugin-caused explosive launches (#13270) #13328

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Fix: clamp excessive entity velocities to [-4,4] to prevent plugin-caused explosive launches (#13270) #13328

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16 changes: 15 additions & 1 deletion paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java
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Original file line number Diff line number Diff line change
Expand Up @@ -200,11 +200,19 @@ public void setVelocity(Vector velocity) {
Preconditions.checkArgument(velocity != null, "velocity");
velocity.checkFinite();
// Paper start - Warn server owners when plugins try to set super high velocities
// and clamp overly large velocities for non-projectile / non-minecart entities to
// avoid extreme physics/networking behaviour introduced by very large motion values.
if (!(this instanceof org.bukkit.entity.Projectile || this instanceof org.bukkit.entity.Minecart) && isUnsafeVelocity(velocity)) {
CraftServer.excessiveVelEx = new Exception("Excessive velocity set detected: tried to set velocity of entity " + entity.getScoreboardName() + " id #" + getEntityId() + " to (" + velocity.getX() + "," + velocity.getY() + "," + velocity.getZ() + ").");
// Clamp velocity to a sane maximum to retain direction while preventing extreme values
double clampedX = clamp(velocity.getX(), -4.0D, 4.0D);
double clampedY = clamp(velocity.getY(), -4.0D, 4.0D);
double clampedZ = clamp(velocity.getZ(), -4.0D, 4.0D);
this.entity.setDeltaMovement(CraftVector.toVec3(new Vector(clampedX, clampedY, clampedZ)));
} else {
this.entity.setDeltaMovement(CraftVector.toVec3(velocity));
}
// Paper end
this.entity.setDeltaMovement(CraftVector.toVec3(velocity));
this.entity.hurtMarked = true;
}

Expand All @@ -231,6 +239,12 @@ private static boolean isUnsafeVelocity(Vector vel) {
return false;
}

private static double clamp(double value, double min, double max) {
if (value < min) return min;
if (value > max) return max;
return value;
}

@Override
public double getHeight() {
return this.getHandle().getBbHeight();
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