diff --git a/app/apps/keys/certificates.py b/app/apps/keys/certificates.py
index e8f902b..cb7e957 100644
--- a/app/apps/keys/certificates.py
+++ b/app/apps/keys/certificates.py
@@ -83,6 +83,7 @@ def _sign_public_key(
     serial: int,
     validity_days: int,
     comment: str,
+    validity_override: str | None = None,
 ) -> str:
     if not ca_private_key or not ca_public_key:
         raise RuntimeError("CA material missing")
@@ -102,7 +103,7 @@ def _sign_public_key(
             "-n",
             principal,
             "-V",
-            f"+{validity_days}d",
+            validity_override or f"+{validity_days}d",
             "-z",
             str(serial),
             pubkey_path,
diff --git a/app/apps/servers/consumers.py b/app/apps/servers/consumers.py
index 5925d0e..bf3b2d1 100644
--- a/app/apps/servers/consumers.py
+++ b/app/apps/servers/consumers.py
@@ -8,6 +8,7 @@ import tempfile
 
 from channels.db import database_sync_to_async
 from channels.generic.websocket import AsyncWebsocketConsumer
+from django.conf import settings
 from django.utils import timezone
 
 from apps.audit.matching import find_matching_event_type
@@ -108,7 +109,8 @@ class ShellConsumer(AsyncWebsocketConsumer):
     async def _start_ssh(self, user):
         # Generate a short-lived keypair + SSH certificate and then
         # bridge the WebSocket to an SSH subprocess.
-        self.tempdir = tempfile.TemporaryDirectory(prefix="keywarden-shell-")
+        temp_base = "/dev/shm" if os.path.isdir("/dev/shm") and os.access("/dev/shm", os.W_OK) else None
+        self.tempdir = tempfile.TemporaryDirectory(prefix="keywarden-shell-", dir=temp_base)
         key_path, cert_path = await asyncio.to_thread(
             _generate_session_keypair,
             self.tempdir.name,
@@ -152,6 +154,13 @@ class ShellConsumer(AsyncWebsocketConsumer):
             stdout=asyncio.subprocess.PIPE,
             stderr=asyncio.subprocess.STDOUT,
         )
+        for path in (key_path, cert_path, f"{key_path}.pub"):
+            try:
+                os.remove(path)
+            except FileNotFoundError:
+                continue
+            except Exception:
+                pass
         self.reader_task = asyncio.create_task(self._stream_output())
 
     async def _stream_output(self):
@@ -246,6 +255,7 @@ def _generate_session_keypair(tempdir: str, user, principal: str) -> tuple[str,
         raise RuntimeError("ssh-keygen not available") from exc
     except subprocess.CalledProcessError as exc:
         raise RuntimeError(f"ssh-keygen failed: {exc.stderr.decode('utf-8', 'ignore')}") from exc
+    os.chmod(key_path, 0o600)
     pubkey_path = key_path + ".pub"
     with open(pubkey_path, "r", encoding="utf-8") as handle:
         public_key = handle.read().strip()
@@ -257,6 +267,7 @@ def _generate_session_keypair(tempdir: str, user, principal: str) -> tuple[str,
         principal=principal,
         serial=serial,
         validity_days=1,
+        validity_override=f"+{settings.KEYWARDEN_SHELL_CERT_VALIDITY_MINUTES}m",
         comment=identity,
     )
     cert_path = key_path + "-cert.pub"
diff --git a/app/keywarden/settings/base.py b/app/keywarden/settings/base.py
index 93db7d0..0554199 100644
--- a/app/keywarden/settings/base.py
+++ b/app/keywarden/settings/base.py
@@ -103,6 +103,7 @@ SESSION_CACHE_ALIAS = "default"
 
 KEYWARDEN_AGENT_CERT_VALIDITY_DAYS = int(os.getenv("KEYWARDEN_AGENT_CERT_VALIDITY_DAYS", "90"))
 KEYWARDEN_USER_CERT_VALIDITY_DAYS = int(os.getenv("KEYWARDEN_USER_CERT_VALIDITY_DAYS", "30"))
+KEYWARDEN_SHELL_CERT_VALIDITY_MINUTES = int(os.getenv("KEYWARDEN_SHELL_CERT_VALIDITY_MINUTES", "15"))
 KEYWARDEN_ACCOUNT_USERNAME_TEMPLATE = os.getenv(
     "KEYWARDEN_ACCOUNT_USERNAME_TEMPLATE", "{{username}}_{{user_id}}"
 )