Libssh2

Pre-authentication remote code execution in libssh2 1.11.1 and earlier allows a malicious SSH server to compromise any connecting client. A heap buffer overflow in the Encrypt-then-MAC (ETM) cipher negotiation path overwrites heap metadata, enabling tcache bin confusion and function pointer control before user authentication. No active exploitation is known, and EPSS is low (0.32%), but the client-side impact is severe if a victim can be lured to an attacker-controlled server.

Memory corruption in libssh2's publickey response parser allows a malicious SSH server to leak heap pointers and corrupt the heap, potentially leading to remote code execution. The issue affects libssh2 versions up to 1.11.1 and is triggered when a client connects to an attacker-controlled SSH server and fetches public keys, with no authentication required on the server side. A patch is available in commit a13bb6c, though no tagged release includes the fix yet; no active exploitation or public exploit code is currently reported.

Client-side denial-of-service in libssh2 through 1.11.1 allows a malicious SSH server to crash any connecting client before authentication by triggering an integer underflow during AES-GCM cipher negotiation, causing an out-of-bounds read and a near-SIZE_MAX memcpy that immediately terminates the process.

Double-free heap corruption in libssh2's SFTP client allows a malicious SSH server to corrupt the memory of any authenticated client that opens an SFTP session. This vulnerability, present in libssh2 through 1.11.1, can be triggered via a crafted server response during the `sftp_open()` operation, leading to tcache poisoning and potential arbitrary code execution on the client. No active exploitation has been confirmed, and no public PoC is known at this time, though the EPSS score is low (0.29%).

Free of an uninitialized, attacker-influenceable pointer in libssh2 through 1.11.1 allows a malicious SSH server to corrupt memory in any connecting client that uses the publickey subsystem. The publickey list is grown via SSH2_REALLOC without zero-initializing new entries, so a server-induced parse failure that reaches the cleanup path causes libssh2_publickey_list_free to operate on an uninitialized attrs pointer. Publicly available exploit code exists (reported by VulnCheck); no public evidence of active exploitation, and it is not listed in CISA KEV.

Heap buffer overflow in the libssh2 SSH client library (all versions through 1.11.1) lets a malicious or compromised SSH server corrupt memory in any connecting client on 32-bit platforms. The publickey subsystem reads an attacker-supplied 32-bit attribute count and multiplies it by the attribute structure size without bounds checking, so the allocation integer-overflows to an undersized buffer that the parsing loop then writes past. Publicly available exploit code exists; this is a CWE-190 integer overflow with no public exploit identified in CISA KEV, so it is not confirmed actively exploited.

Out-of-bounds heap read in libssh2 through 1.11.1 enables a malicious SFTP server or man-in-the-middle attacker to leak heap memory or crash client applications by sending a crafted SSH_FXP_NAME response with an inflated link_len during READLINK or REALPATH operations. The library is embedded in many SSH/SFTP clients (curl, Git tooling, language bindings), so impact extends to anywhere libssh2 is used as a client. No public exploit identified at time of analysis, but a vendor patch (commit 2dae302) is available and the issue was reported by VulnCheck.

Remote code execution in libssh2 through version 1.11.1 stems from an unchecked packet_length field in ssh2_transport_read() that allows attackers to send oversized SSH packets and corrupt heap memory. The flaw was reported by VulnCheck and is fixed upstream in commit 97acf3df (PR #2052), which adds an upper-bound check against LIBSSH2_PACKET_MAXPAYLOAD. No public exploit has been identified at time of analysis, but the CVSS 4.0 score of 9.2 reflects pre-authentication network reach with high impact on confidentiality, integrity, and availability.

Pre-authentication denial of service in libssh2 through 1.11.1 allows a malicious SSH server to pin a connecting client's CPU at 100% for over 60 seconds by advertising an attacker-controlled SSH_MSG_EXT_INFO extension count of 0xFFFFFFFF during key exchange. The flaw is reachable before authentication completes, so any client that initiates an SSH session to a hostile or compromised server endpoint is exposed, and no public exploit identified at time of analysis though VulnCheck has published an advisory and the upstream PR diff is public.

Integer overflow in libssh2 up to version 1.11.1 allows remote unauthenticated attackers to cause memory corruption during SSH password authentication. The vulnerability exists in the userauth_password function where inadequate bounds checking on username_len and password_len parameters can trigger integer overflow when calculating buffer sizes, potentially leading to confidentiality breach, integrity compromise, and service disruption. Upstream fix available via GitHub commit 256d04b60d80bf1190e96b0ad1e91b2174d744b1. No active exploitation confirmed (not in CISA KEV), but publicly accessible patch reveals exact exploitation technique.

The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6 and other products, allows remote attackers to bypass integrity checks such that some packets are omitted (from. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. Public exploit code available and EPSS exploitation probability 53.6%.

In libssh2 v1.9.0 and earlier versions, the SSH_MSG_DISCONNECT logic in packet.c has an integer overflow in a bounds check, enabling an attacker to specify an arbitrary (out-of-bounds) offset for a. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

In libssh2 before 1.9.0, kex_method_diffie_hellman_group_exchange_sha256_key_exchange in kex.c has an integer overflow that could lead to an out-of-bounds read in the way packets are read from the. Rated high severity (CVSS 8.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available and no vendor patch available.

An out of bounds read flaw was discovered in libssh2 before 1.8.1 in the way SSH packets with a padding length value greater than the packet length are parsed. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.

An out of bounds read flaw was discovered in libssh2 before 1.8.1 in the way SFTP packets with empty payloads are parsed. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.

An integer overflow flaw which could lead to an out of bounds write was discovered in libssh2 before 1.8.1 in the way SSH_MSG_CHANNEL_REQUEST packets with an exit signal are parsed. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

An integer overflow flaw, which could lead to an out of bounds write, was discovered in libssh2 before 1.8.1 in the way keyboard prompt requests are parsed. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

A flaw was found in libssh2 before 1.8.1 creating a vulnerability on the SSH client side. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Integer Overflow vulnerability could allow attackers to cause unexpected behavior through arithmetic overflow.

An out of bounds read flaw was discovered in libssh2 before 1.8.1 when a specially crafted SFTP packet is received from the server. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.

An integer overflow flaw which could lead to an out of bounds write was discovered in libssh2 before 1.8.1 in the way packets are read from the server. Rated high severity (CVSS 8.8), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

An out of bounds read flaw was discovered in libssh2 before 1.8.1 in the way SSH_MSG_CHANNEL_REQUEST packets with an exit status message and no payload are parsed. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity.

An out of bounds read flaw was discovered in libssh2 before 1.8.1 in the _libssh2_packet_require and _libssh2_packet_requirev functions. Rated critical severity (CVSS 9.1), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Out-of-bounds Read vulnerability could allow attackers to read data from memory outside the intended buffer boundaries.

The diffie_hellman_sha256 function in kex.c in libssh2 before 1.7.0 improperly truncates secrets to 128 or 256 bits, which makes it easier for man-in-the-middle attackers to decrypt or intercept SSH. Rated medium severity (CVSS 5.9), this vulnerability is remotely exploitable, no authentication required. This Exposure of Sensitive Information vulnerability could allow attackers to access sensitive data that should not be disclosed.

The kex_agree_methods function in libssh2 before 1.5.0 allows remote servers to cause a denial of service (crash) or have other unspecified impact via crafted length values in an SSH_MSG_KEXINIT. Rated medium severity (CVSS 6.8), this vulnerability is remotely exploitable. No vendor patch available.