diff --git a/fixtures/credhub-test-app/go.mod b/fixtures/credhub-test-app/go.mod
index 25c63c3..03b8f82 100644
--- a/fixtures/credhub-test-app/go.mod
+++ b/fixtures/credhub-test-app/go.mod
@@ -10,7 +10,7 @@ require (
 	github.com/cloudfoundry/go-socks5 v0.0.0-20240831012420-2590b55236ee // indirect
 	github.com/cloudfoundry/socks5-proxy v0.2.131 // indirect
 	github.com/hashicorp/go-version v1.7.0 // indirect
-	golang.org/x/crypto v0.29.0 // indirect
+	golang.org/x/crypto v0.31.0 // indirect
 	golang.org/x/net v0.31.0 // indirect
-	golang.org/x/sys v0.27.0 // indirect
+	golang.org/x/sys v0.28.0 // indirect
 )
diff --git a/fixtures/credhub-test-app/go.sum b/fixtures/credhub-test-app/go.sum
index 6bd40dc..2228417 100644
--- a/fixtures/credhub-test-app/go.sum
+++ b/fixtures/credhub-test-app/go.sum
@@ -19,16 +19,16 @@ github.com/onsi/ginkgo/v2 v2.21.0 h1:7rg/4f3rB88pb5obDgNZrNHrQ4e6WpjonchcpuBRnZM
 github.com/onsi/ginkgo/v2 v2.21.0/go.mod h1:7Du3c42kxCUegi0IImZ1wUQzMBVecgIHjR1C+NkhLQo=
 github.com/onsi/gomega v1.35.1 h1:Cwbd75ZBPxFSuZ6T+rN/WCb/gOc6YgFBXLlZLhC7Ds4=
 github.com/onsi/gomega v1.35.1/go.mod h1:PvZbdDc8J6XJEpDK4HCuRBm8a6Fzp9/DmhC9C7yFlog=
-golang.org/x/crypto v0.29.0 h1:L5SG1JTTXupVV3n6sUqMTeWbjAyfPwoda2DLX8J8FrQ=
-golang.org/x/crypto v0.29.0/go.mod h1:+F4F4N5hv6v38hfeYwTdx20oUvLLc+QfrE9Ax9HtgRg=
+golang.org/x/crypto v0.31.0 h1:ihbySMvVjLAeSH1IbfcRTkD/iNscyz8rGzjF/E5hV6U=
+golang.org/x/crypto v0.31.0/go.mod h1:kDsLvtWBEx7MV9tJOj9bnXsPbxwJQ6csT/x4KIN4Ssk=
 golang.org/x/net v0.31.0 h1:68CPQngjLL0r2AlUKiSxtQFKvzRVbnzLwMUn5SzcLHo=
 golang.org/x/net v0.31.0/go.mod h1:P4fl1q7dY2hnZFxEk4pPSkDHF+QqjitcnDjUQyMM+pM=
-golang.org/x/sys v0.27.0 h1:wBqf8DvsY9Y/2P8gAfPDEYNuS30J4lPHJxXSb/nJZ+s=
-golang.org/x/sys v0.27.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/term v0.26.0 h1:WEQa6V3Gja/BhNxg540hBip/kkaYtRg3cxg4oXSw4AU=
-golang.org/x/term v0.26.0/go.mod h1:Si5m1o57C5nBNQo5z1iq+XDijt21BDBDp2bK0QI8e3E=
-golang.org/x/text v0.20.0 h1:gK/Kv2otX8gz+wn7Rmb3vT96ZwuoxnQlY+HlJVj7Qug=
-golang.org/x/text v0.20.0/go.mod h1:D4IsuqiFMhST5bX19pQ9ikHC2GsaKyk/oF+pn3ducp4=
+golang.org/x/sys v0.28.0 h1:Fksou7UEQUWlKvIdsqzJmUmCX3cZuD2+P3XyyzwMhlA=
+golang.org/x/sys v0.28.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/term v0.27.0 h1:WP60Sv1nlK1T6SupCHbXzSaN0b9wUmsPoRS9b61A23Q=
+golang.org/x/term v0.27.0/go.mod h1:iMsnZpn0cago0GOrHO2+Y7u7JPn5AylBrcoWkElMTSM=
+golang.org/x/text v0.21.0 h1:zyQAAkrwaneQ066sspRyJaG9VNi/YJ1NfzcGB3hZ/qo=
+golang.org/x/text v0.21.0/go.mod h1:4IBbMaMmOPCJ8SecivzSH54+73PCFmPWxNTLm+vZkEQ=
 golang.org/x/tools v0.27.0 h1:qEKojBykQkQ4EynWy4S8Weg69NumxKdn40Fce3uc/8o=
 golang.org/x/tools v0.27.0/go.mod h1:sUi0ZgbwW9ZPAq26Ekut+weQPR5eIM6GQLQ1Yjm1H0Q=
 google.golang.org/protobuf v1.35.2 h1:8Ar7bF+apOIoThw1EdZl0p1oWvMqTHmpA2fRTyZO8io=
diff --git a/fixtures/credhub-test-app/vendor/golang.org/x/crypto/ssh/server.go b/fixtures/credhub-test-app/vendor/golang.org/x/crypto/ssh/server.go
index c0d1c29..5b5ccd9 100644
--- a/fixtures/credhub-test-app/vendor/golang.org/x/crypto/ssh/server.go
+++ b/fixtures/credhub-test-app/vendor/golang.org/x/crypto/ssh/server.go
@@ -149,7 +149,7 @@ func (s *ServerConfig) AddHostKey(key Signer) {
 }
 
 // cachedPubKey contains the results of querying whether a public key is
-// acceptable for a user.
+// acceptable for a user. This is a FIFO cache.
 type cachedPubKey struct {
 	user       string
 	pubKeyData []byte
@@ -157,7 +157,13 @@ type cachedPubKey struct {
 	perms      *Permissions
 }
 
-const maxCachedPubKeys = 16
+// maxCachedPubKeys is the number of cache entries we store.
+//
+// Due to consistent misuse of the PublicKeyCallback API, we have reduced this
+// to 1, such that the only key in the cache is the most recently seen one. This
+// forces the behavior that the last call to PublicKeyCallback will always be
+// with the key that is used for authentication.
+const maxCachedPubKeys = 1
 
 // pubKeyCache caches tests for public keys.  Since SSH clients
 // will query whether a public key is acceptable before attempting to
@@ -179,9 +185,10 @@ func (c *pubKeyCache) get(user string, pubKeyData []byte) (cachedPubKey, bool) {
 
 // add adds the given tuple to the cache.
 func (c *pubKeyCache) add(candidate cachedPubKey) {
-	if len(c.keys) < maxCachedPubKeys {
-		c.keys = append(c.keys, candidate)
+	if len(c.keys) >= maxCachedPubKeys {
+		c.keys = c.keys[1:]
 	}
+	c.keys = append(c.keys, candidate)
 }
 
 // ServerConn is an authenticated SSH connection, as seen from the
diff --git a/fixtures/credhub-test-app/vendor/modules.txt b/fixtures/credhub-test-app/vendor/modules.txt
index 30517c4..138f724 100644
--- a/fixtures/credhub-test-app/vendor/modules.txt
+++ b/fixtures/credhub-test-app/vendor/modules.txt
@@ -17,7 +17,7 @@ github.com/cloudfoundry/socks5-proxy
 # github.com/hashicorp/go-version v1.7.0
 ## explicit
 github.com/hashicorp/go-version
-# golang.org/x/crypto v0.29.0
+# golang.org/x/crypto v0.31.0
 ## explicit; go 1.20
 golang.org/x/crypto/blowfish
 golang.org/x/crypto/chacha20
@@ -31,6 +31,6 @@ golang.org/x/crypto/ssh/internal/bcrypt_pbkdf
 golang.org/x/net/context
 golang.org/x/net/internal/socks
 golang.org/x/net/proxy
-# golang.org/x/sys v0.27.0
+# golang.org/x/sys v0.28.0
 ## explicit; go 1.18
 golang.org/x/sys/cpu