From f91f7a7c31bf90b39c1de895ad116a2bacc88748 Mon Sep 17 00:00:00 2001
From: Neal Patel <nealpatel@google.com>
Date: Wed, 10 Sep 2025 14:27:42 -0400
Subject: [PATCH] ssh/agent: prevent panic on malformed constraint

An attacker could supply a malformed Constraint that
would trigger a panic in a serving agent, effectively
causing denial of service.

Thank you to Jakub Ciolek for reporting this issue.

Fixes CVE-2025-47914
Fixes golang/go#76364

Change-Id: I195bbc68b1560d4f04897722a6a653a7cbf086eb
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/721960
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Roland Shoemaker <roland@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>
---

diff --git a/vendor/golang.org/x/crypto/ssh/agent/server.go b/vendor/golang.org/x/crypto/ssh/agent/server.go
index 88ce4da..4e8ff86 100644
--- a/vendor/golang.org/x/crypto/ssh/agent/server.go
+++ b/vendor/golang.org/x/crypto/ssh/agent/server.go
@@ -203,6 +203,9 @@
 	for len(constraints) != 0 {
 		switch constraints[0] {
 		case agentConstrainLifetime:
+			if len(constraints) < 5 {
+				return 0, false, nil, io.ErrUnexpectedEOF
+			}
 			lifetimeSecs = binary.BigEndian.Uint32(constraints[1:5])
 			constraints = constraints[5:]
 		case agentConstrainConfirm: