--- /dev/null
+From d1b6996c3b31ce6b60d5a820ecc33880e61ef0ae Mon Sep 17 00:00:00 2001
+From: Viktor Szakats <commit@vsz.me>
+Date: Thu, 23 Jul 2026 10:32:04 +0200
+Subject: [PATCH] openssl: fix potential OOB read/write with AES-GCM in
+ `ssh2_cipher_crypt()`
+
+By applying two bounds checks to non-debug builds.
+
+Reported-by: Vladimir Eli Tokarev
+Fixes GHSA-c4f7-cvfc-33j7
+Follow-up to 3c953c05d67eb1ebcfd3316f279f12c4b1d600b4 #797
+
+Closes #2401
+
+CVE: CVE-2026-66033
+Upstream-Status: Backport [https://github.com/libssh2/libssh2/commit/a2ed82d40964bbc0d64cd717aa0a5a892117d2e6]
+Signed-off-by: Jaipaul Cheernam <jaipaul.cheernam@est.tech>
+---
+ src/openssl.c | 10 ++++++----
+ 1 file changed, 6 insertions(+), 4 deletions(-)
+
+diff --git a/src/openssl.c b/src/openssl.c
+index eba05031..28ae1cc0 100644
+--- a/src/openssl.c
++++ b/src/openssl.c
+@@ -1042,13 +1042,15 @@ _libssh2_cipher_crypt(_libssh2_cipher_ctx * ctx,
+ const int aadlen = (is_aesgcm && IS_FIRST(firstlast)) ? 4 : 0;
+ /* size of AT, if present */
+ const int authenticationtag = IS_LAST(firstlast) ? authlen : 0;
+- /* length to encrypt */
+- const int cryptlen = (unsigned int)blocksize - aadlen - authenticationtag;
++ unsigned int cryptlen; /* length to encrypt */
+
+ (void)algo;
+
+- assert(blocksize <= sizeof(buf));
+- assert(cryptlen >= 0);
++ if(blocksize > sizeof(buf) ||
++ blocksize < (size_t)(aadlen + authenticationtag))
++ return 1;
++
++ cryptlen = (unsigned int)blocksize - aadlen - authenticationtag;
+
+ #if LIBSSH2_AES_GCM
+ /* First block */