Russh: client wrong-length X25519 `clone_from_slice` panic (pre-auth DoS)

Summary A malicious SSH server can crash a russh client session with a single malformed key-exchange reply, causing a pre-authentication Denial-of-Service before the server host key is verified. The embedding process itself stays up, but the connection is killed deterministically. Details Every...

GHSA-5XVQ-CP9X-6P6R Russh: Pre-auth remote panic via all-zero Curve25519 peer public value (encode_mpint OOB)

A pre-authentication denial-of-service panic in russh 0.62.2 commit c4be19f1915c8682f4615c3fd50008512b474491, current default branch main as of 2026-07-22. An unauthenticated client sends a single SSHMSGKEXECDHINIT whose QC is 32 zero bytes. russh's Curve25519 KEX does not reject the all-zero pee...

CVE-2026-66035

CVE-2026-66035 affects libssh2 up to 1.11.1 and was fixed in commit 42e33d8. The vulnerability is a pre-authentication heap buffer overflow in the Encrypt-then-MAC (ETM) cipher negotiation path. In libssh2’s fullpacket() implemented under src/transport.c, the ETM code path allocates a buffer of p...

EUVD-2026-48722

libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packetlength smaller than the cipher's block size during Encrypt-then-M...

CVE-2026-66035 libssh2 Heap Buffer Overflow via ETM Cipher Negotiation

libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packetlength smaller than the cipher's block size during Encrypt-then-M...

CVE-2026-66035 libssh2 Heap Buffer Overflow via ETM Cipher Negotiation

libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packetlength smaller than the cipher's block size during Encrypt-then-M...

CVE-2026-66035 libssh2 Heap Buffer Overflow via ETM Cipher Negotiation

libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packetlength smaller than the cipher's block size during Encrypt-then-M...

CVE-2026-66035

libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packetlength smaller than the cipher's block size during Encrypt-then-M...

CVE-2026-66035

libssh2 through 1.11.1, fixed in commit 42e33d8, contains a pre-authentication heap buffer overflow vulnerability that allows a malicious SSH server to corrupt heap metadata in any connecting client by sending a packet with a packetlength smaller than the cipher's block size during Encrypt-then-M...

CVE-2026-66033

libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2ciphercrypt function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit...

CVE-2026-66033

CVE-2026-66033 affects libssh2 up to 1.11.1. A pre-authentication integer underflow in the ssh2_cipher_crypt() function (src/openssl.c) allows a malicious SSH server to crash a connecting client during handshake by negotiating AES-GCM ciphers. The underflow (blocksize − aadlen − taglen) can trigg...

CVE-2026-66033 libssh2 Integer Underflow DoS via AES-GCM Cipher Negotiation

libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2ciphercrypt function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit...

CVE-2026-66033

libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2ciphercrypt function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit...

CVE-2026-66033 libssh2 Integer Underflow DoS via AES-GCM Cipher Negotiation

libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2ciphercrypt function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit...

CVE-2026-66033 libssh2 Integer Underflow DoS via AES-GCM Cipher Negotiation

libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2ciphercrypt function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit...

CVE-2026-66033

libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2ciphercrypt function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit...

EUVD-2026-48720

libssh2 through 1.11.1, fixed in commit a2ed82d, contains a pre-authentication integer underflow vulnerability in the ssh2ciphercrypt function in src/openssl.c that allows a malicious SSH server to crash any connecting client by negotiating AES-GCM ciphers during handshake. Attackers can exploit...

PT-2026-64382

Name of the Vulnerable Software and Affected Versions libssh2 versions prior to 1.11.1 Description A pre-authentication heap buffer overflow occurs during Encrypt-then-MAC ETM cipher negotiation. A malicious SSH server can corrupt heap metadata in a connecting client by sending a packet where the...

PT-2026-64380

Name of the Vulnerable Software and Affected Versions libssh2 versions prior to 1.11.1 Description A pre-authentication integer underflow exists in the ssh2 cipher crypt function within src/openssl.c. A malicious SSH server can trigger this issue during the handshake by negotiating AES-GCM cipher...

openssh: Fix of CVE-2026-60000

CVE-2026-60000: fix GSSAPI pre-authentication denial of service where inputgssapierrtok did not finish the postponed authentication attempt, so failed GSSAPI requests were never counted against MaxAuthTries...