Vulnerabilidades

rsync 3.2.0 through 3.2.3 (openssl mode) and rsync-ssl through 3.4.4 (stunnel mode) contain a TLS certificate validation vulnerability that allows on-path attackers to intercept encrypted sessions by presenting self-signed or otherwise invalid certificates. Attackers can exploit the failure to validate server TLS…

A stack-based out-of-bounds read vulnerability exists in the "s_vlog" function of stunnel, when handling oversized log messages via "vsnprintf". A remote attacker with network access to a stunnel service can send protocol inputs that trigger a log message longer than 1024 bytes, leading to an out-of-bounds stack read…

A Server-Side Request Forgery (SSRF) bypass vulnerability exists in “stunnel” 5.79 and lower when configured in SOCKS proxy mode. This flaw allows a client to bypass intended localhost restrictions by using IPv4-mapped IPv6 addresses (e.g., “::ffff:127.0.0.1”) or unspecified addresses ("0.0.0.0", "::"), enabling…

A flaw was found in stunnel before 5.57, where it improperly validates client certificates when it is configured to use both redirect and verifyChain options. This flaw allows an attacker with a certificate signed by a Certificate Authority, which is not the one accepted by the stunnel server, to access the tunneled…

Stunnel 5.00 through 5.13, when using the redirect option, does not redirect client connections to the expected server after the initial connection, which allows remote attackers to bypass authentication.

stunnel before 5.00, when using fork threading, does not properly update the state of the OpenSSL pseudo-random number generator (PRNG), which causes subsequent children with the same process ID to use the same entropy pool and allows remote attackers to obtain private keys for EC (ECDSA) or DSA certificates.

stunnel 4.21 through 4.54, when CONNECT protocol negotiation and NTLM authentication are enabled, does not correctly perform integer conversion, which allows remote proxy servers to execute arbitrary code via a crafted request that triggers a buffer overflow.

stunnel 4.40 and 4.41 might allow remote attackers to execute arbitrary code or cause a denial of service (heap memory corruption) via unspecified vectors.

The OCSP functionality in stunnel before 4.24 does not properly search certificate revocation lists (CRL), which allows remote attackers to bypass intended access restrictions by using revoked certificates.

Unspecified vulnerability in stunnel before 4.23, when running as a service on Windows, allows local users to gain privileges via unknown attack vectors.

Stunnel 4.00, and 3.24 and earlier, leaks a privileged file descriptor returned by listen(), which allows local users to hijack the Stunnel server.

stunnel 4.0.3 and earlier allows attackers to cause a denial of service (crash) via SIGCHLD signal handler race conditions that cause an inconsistency in the child counter.

OpenSSL does not use RSA blinding by default, which allows local and remote attackers to obtain the server's private key by determining factors using timing differences on (1) the number of extra reductions during Montgomery reduction, and (2) the use of different integer multiplication algorithms ("Karatsuba" and…

Format string vulnerability in stunnel before 3.22 when used in client mode for (1) smtp, (2) pop, or (3) nntp allows remote malicious servers to execute arbitrary code.

Format string vulnerability in stunnel 3.8 and earlier allows attackers to execute arbitrary commands via a malformed ident username.