From cf7f15af0cb23ddc24835d6cfb642c0388b1e388 Mon Sep 17 00:00:00 2001
From: PobreGato <315121269+pobregat0@users.noreply.github.com>
Date: Wed, 9 Sep 2026 19:48:40 -0400
Subject: [PATCH] check the whole block header fits before reading block size
 in SSU2 payload

---
 libi2pd/SSU2Session.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/libi2pd/SSU2Session.cpp b/libi2pd/SSU2Session.cpp
index 71b2b19c..5b4dee48 100644
--- a/libi2pd/SSU2Session.cpp
+++ b/libi2pd/SSU2Session.cpp
@@ -1780,7 +1780,9 @@ namespace transport
 	void SSU2Session::HandlePayload (const uint8_t * buf, size_t len)
 	{
 		size_t offset = 0;
-		while (offset < len)
+		// the block header is three bytes: without all of them the size field below
+		// would be read past the end of the payload
+		while (offset + 3 <= len)
 		{
 			uint8_t blk = buf[offset];
 			offset++;