diff --git a/CHANGELOG.next.asciidoc b/CHANGELOG.next.asciidoc
index 9d3a3a92c72..e2a07b3fe3a 100644
--- a/CHANGELOG.next.asciidoc
+++ b/CHANGELOG.next.asciidoc
@@ -78,6 +78,7 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 
 *Packetbeat*
 
+- Expire source port mappings. {pull}41581[41581]
 
 *Winlogbeat*
 
diff --git a/packetbeat/procs/procs.go b/packetbeat/procs/procs.go
index 11b9fc2e8d8..f578b49a5d4 100644
--- a/packetbeat/procs/procs.go
+++ b/packetbeat/procs/procs.go
@@ -64,6 +64,7 @@ type portProcMapping struct {
 	endpoint endpoint // FIXME: This is never used.
 	pid      int
 	proc     *process
+	expires  time.Time
 }
 
 // process describes an OS process.
@@ -185,8 +186,8 @@ func (proc *ProcessesWatcher) isLocalIP(ip net.IP) bool {
 
 func (proc *ProcessesWatcher) findProc(address net.IP, port uint16, transport applayer.Transport) *process {
 	proc.mu.Lock()
+	defer proc.mu.Unlock()
 	procMap, ok := proc.portProcMap[transport]
-	proc.mu.Unlock()
 	if !ok {
 		return nil
 	}
@@ -206,24 +207,47 @@ func (proc *ProcessesWatcher) findProc(address net.IP, port uint16, transport ap
 	return nil
 }
 
-func lookupMapping(address net.IP, port uint16, procMap map[endpoint]portProcMapping) (p portProcMapping, found bool) {
+// proc.mu must be locked
+func lookupMapping(address net.IP, port uint16, procMap map[endpoint]portProcMapping) (portProcMapping, bool) {
+	now := time.Now()
+	key := endpoint{address.String(), port}
+	p, found := procMap[key]
+
 	// Precedence when one socket is bound to a specific IP:port and another one
 	// to INADDR_ANY and same port is not clear. Seems that the last one to bind
 	// takes precedence, and we don't have a way to tell.
 	// This function takes the naive approach of giving precedence to the more
 	// specific address and then to INADDR_ANY.
-	if p, found = procMap[endpoint{address.String(), port}]; found {
-		return p, found
+	if !found {
+		if address.To4() != nil {
+			key.address = anyIPv4
+		} else {
+			key.address = anyIPv6
+		}
+
+		p, found = procMap[key]
 	}
 
-	nullAddr := anyIPv4
-	if asIPv4 := address.To4(); asIPv4 == nil {
-		nullAddr = anyIPv6
+	// We can't guarantee `p` doesn't point to an old entry, since
+	// we never remove entries from `procMap`, we only overwrite
+	// them, but we only overwrite them once an unrelated packet
+	// that doesn't have an entry on `procMap` ends up rebuilding
+	// the whole map.
+	//
+	// We take a conservative approach by discarding the entry if
+	// it's old enough. When we fail the first time here, our caller
+	// updates all maps and calls us again.
+	if found && now.After(p.expires) {
+		logp.Debug("procs", "PID %d (%s) port %d is too old, discarding", p.pid, p.proc.name, port)
+		delete(procMap, key)
+		p = portProcMapping{}
+		found = false
 	}
-	p, found = procMap[endpoint{nullAddr, port}]
+
 	return p, found
 }
 
+// proc.mu must be locked
 func (proc *ProcessesWatcher) updateMap(transport applayer.Transport) {
 	if logp.HasSelector("procsdetailed") {
 		start := time.Now()
@@ -244,6 +268,7 @@ func (proc *ProcessesWatcher) updateMap(transport applayer.Transport) {
 	}
 }
 
+// proc.mu must be locked
 func (proc *ProcessesWatcher) expireProcessCache() {
 	now := time.Now()
 	for pid, info := range proc.processCache {
@@ -253,9 +278,8 @@ func (proc *ProcessesWatcher) expireProcessCache() {
 	}
 }
 
+// proc.mu must be locked
 func (proc *ProcessesWatcher) updateMappingEntry(transport applayer.Transport, e endpoint, pid int) {
-	proc.mu.Lock()
-	defer proc.mu.Unlock()
 	prev, ok := proc.portProcMap[transport][e]
 	if ok && prev.pid == pid {
 		// This port->pid mapping already exists
@@ -267,11 +291,21 @@ func (proc *ProcessesWatcher) updateMappingEntry(transport applayer.Transport, e
 		return
 	}
 
-	// Simply overwrite old entries for now.
-	// We never expire entries from this map. Since there are 65k possible
-	// ports, the size of the dict can be max 1.5 MB, which we consider
-	// reasonable.
-	proc.portProcMap[transport][e] = portProcMapping{endpoint: e, pid: pid, proc: p}
+	// We overwrite previous entries here, and they expire in
+	// lookupMapping() if they are deemed old enough.
+	//
+	// Map size is bound by the number of ports: ~65k, so it's
+	// fine to have old entries lingering, as long as we don't
+	// trust them on subsequent connections.
+	//
+	// If the source port is re-used within the hardcoded 10
+	// seconds window, we might end up hitting an old mapping.
+	proc.portProcMap[transport][e] = portProcMapping{
+		endpoint: e,
+		pid:      pid,
+		proc:     p,
+		expires:  time.Now().Add(10 * time.Second),
+	}
 
 	if logp.IsDebug("procsdetailed") {
 		logp.Debug("procsdetailed", "updateMappingEntry(): local=%s:%d/%s pid=%d process='%s'",