Уязвимость функции ares_set_sortlist библиотеки асинхронных DNS-запросов c-ares, позволяющая нарушителю вызвать отказ в обслуживании или оказать ограниченное влияния на конфиденциальность и целостность

A flaw was found in the c-ares package. The ares_set_sortlist is missing checks about the validity of the input string, which allows a possible arbitrary length stack overflow. This issue may cause a denial of service or a limited impact on confidentiality and integrity.

c-ares is an asynchronous resolver library. When cross-compiling c-ares and using the autotools build system, CARES_RANDOM_FILE will not be set, as seen when cross compiling aarch64 android. This will downgrade to using rand() as a fallback which could allow an attacker to take advantage of the lack of entropy by not using a CSPRNG. This issue was patched in version 1.19.1.

c-ares is an asynchronous resolver library. ares_inet_net_pton() is vulnerable to a buffer underflow for certain ipv6 addresses, in particular "0::00:00:00/2" was found to cause an issue. C-ares only uses this function internally for configuration purposes which would require an administrator to configure such an address via ares_set_sortlist(). However, users may externally use ares_inet_net_pton() for other purposes and thus be vulnerable to more severe issues. This issue has been fixed in 1.19.1.

c-ares is an asynchronous resolver library. When /dev/urandom or RtlGenRandom() are unavailable, c-ares uses rand() to generate random numbers used for DNS query ids. This is not a CSPRNG, and it is also not seeded by srand() so will generate predictable output. Input from the random number generator is fed into a non-compilant RC4 implementation and may not be as strong as the original RC4 implementation. No attempt is made to look for modern OS-provided CSPRNGs like arc4random() that is widely available. This issue has been fixed in version 1.19.1.

c-ares is an asynchronous resolver library. c-ares is vulnerable to denial of service. If a target resolver sends a query, the attacker forges a malformed UDP packet with a length of 0 and returns them to the target resolver. The target resolver erroneously interprets the 0 length as a graceful shutdown of the connection. This issue has been patched in version 1.19.1.

Extremely large RSA keys in certificate chains can cause a client/server to expend significant CPU time verifying signatures. With fix, the size of RSA keys transmitted during handshakes is restricted to <= 8192 bits. Based on a survey of publicly trusted RSA keys, there are currently only three certificates in circulation with keys larger than this, and all three appear to be test certificates that are not actively deployed. It is possible there are larger keys in use in private PKIs, but we target the web PKI, so causing breakage here in the interests of increasing the default safety of users of crypto/tls seems reasonable.