[meta-oe][scarthgap][PATCH 1/5] libssh: Fix CVE-2026-59843

From: Hetvi Thakar <[email protected]>

The stable-0.11 commit shown in [1] is the upstream fix selected for
this backport. The upstream advisory [2] documents CVE-2026-59843 and
identifies libssh 0.11.5 as the fixed release for the 0.11 series.

[1] https://git.libssh.org/projects/libssh.git/commit/?id=687ef1c44b646b9db0b1c6e8f987edb7c9e4d919
[2] https://www.libssh.org/security/advisories/CVE-2026-59843.txt

Signed-off-by: Hetvi Thakar <[email protected]>
---
 .../libssh/libssh/CVE-2026-59843.patch        | 84 +++++++++++++++++++
 .../recipes-support/libssh/libssh_0.10.6.bb   |  1 +
 2 files changed, 85 insertions(+)
 create mode 100644 meta-oe/recipes-support/libssh/libssh/CVE-2026-59843.patch

diff --git a/meta-oe/recipes-support/libssh/libssh/CVE-2026-59843.patch b/meta-oe/recipes-support/libssh/libssh/CVE-2026-59843.patch
new file mode 100644
index 0000000000..03d3ce6ea2
--- /dev/null
+++ b/meta-oe/recipes-support/libssh/libssh/CVE-2026-59843.patch
@@ -0,0 +1,84 @@
+From d965eb941a9a83a0643570a93d8997b91e248fc1 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Pavol=20=C5=BD=C3=A1=C4=8Dik?= <[email protected]>
+Date: Fri, 6 Mar 2026 13:58:30 +0100
+Subject: [PATCH] CVE-2026-59843 channels: Fail when receiving max packet size
+ 0
+MIME-Version: 1.0
+Content-Type: text/plain; charset=UTF-8
+Content-Transfer-Encoding: 8bit
+
+Do this both for SSH2_MSG_CHANNEL_OPEN and for
+SSH2_MSG_CHANNEL_OPEN_CONFIRMATION. Using the
+max packet size 0 would lead to an infinite loop
+in channel_write_common.
+
+Originally reported by Rinku Das on on 23th February.
+Independently reported by Yi Lin on 26th February and
+Haruto Kimura on 22nd March.
+
+We do not consider this as a security issue as connecting
+to untrusted servers on the internet brings much worse
+security consequences than hanging your clinet.
+
+Signed-off-by: Pavol Žáčik <[email protected]>
+Reviewed-by: Jakub Jelen <[email protected]>
+
+CVE: CVE-2026-59843
+Upstream-Status: Backport [https://git.libssh.org/projects/libssh.git/commit/?id=687ef1c44b646b9db0b1c6e8f987edb7c9e4d919]
+
+(cherry picked from commit 44b186fa17aff497dae420c59c003222e438103c)
+(cherry picked from commit 687ef1c44b646b9db0b1c6e8f987edb7c9e4d919)
+Signed-off-by: Hetvi Thakar <[email protected]>
+---
+ src/channels.c |  7 +++++++
+ src/messages.c | 19 +++++++++++++++----
+ 2 files changed, 22 insertions(+), 4 deletions(-)
+
+diff --git a/src/channels.c b/src/channels.c
+index 8290dbd1..3afdcf11 100644
+--- a/src/channels.c
++++ b/src/channels.c
+@@ -192,6 +192,13 @@ SSH_PACKET_CALLBACK(ssh_packet_channel_open_conf){
+   if (rc != SSH_OK)
+       goto error;
+ 
++  if (channel->remote_maxpacket == 0) {
++      SSH_LOG(SSH_LOG_RARE,
++              "Invalid maximum packet size 0 in "
++              "SSH2_MSG_CHANNEL_OPEN_CONFIRMATION");
++      goto error;
++  }
++
+   SSH_LOG(SSH_LOG_PROTOCOL,
+       "Received a CHANNEL_OPEN_CONFIRMATION for channel %d:%d",
+       channel->local_channel,
+diff --git a/src/messages.c b/src/messages.c
+index 6dadabf0..e79ecec2 100644
+--- a/src/messages.c
++++ b/src/messages.c
+@@ -1160,10 +1160,21 @@ SSH_PACKET_CALLBACK(ssh_packet_channel_open){
+   SSH_LOG(SSH_LOG_PACKET,
+       "Clients wants to open a %s channel", type_c);
+ 
+-  ssh_buffer_unpack(packet,"ddd",
+-          &msg->channel_request_open.sender,
+-          &msg->channel_request_open.window,
+-          &msg->channel_request_open.packet_size);
++  rc = ssh_buffer_unpack(packet,
++                         "ddd",
++                         &msg->channel_request_open.sender,
++                         &msg->channel_request_open.window,
++                         &msg->channel_request_open.packet_size);
++  if (rc != SSH_OK){
++      goto error;
++  }
++
++  if (msg->channel_request_open.packet_size == 0) {
++      ssh_set_error(session,
++                    SSH_FATAL,
++                    "Invalid maximum packet size 0 in SSH2_MSG_CHANNEL_OPEN");
++      goto error;
++  }
+ 
+   if (session->session_state != SSH_SESSION_STATE_AUTHENTICATED){
+     ssh_set_error(session,SSH_FATAL, "Invalid state when receiving channel open request (must be authenticated)");
diff --git a/meta-oe/recipes-support/libssh/libssh_0.10.6.bb b/meta-oe/recipes-support/libssh/libssh_0.10.6.bb
index 1f64920a50..381b3efc7d 100644
--- a/meta-oe/recipes-support/libssh/libssh_0.10.6.bb
+++ b/meta-oe/recipes-support/libssh/libssh_0.10.6.bb
@@ -32,6 +32,7 @@ SRC_URI = "git://git.libssh.org/projects/libssh.git;protocol=https;branch=stable
            file://CVE-2026-0968-2.patch \
            file://CVE-2026-0967.patch \
            file://CVE-2026-0965.patch \
+           file://CVE-2026-59843.patch \
           "
 SRCREV = "10e09e273f69e149389b3e0e5d44b8c221c2e7f6"
 
-- 
2.35.6