CVE-2014-0016: Medium severity Stunnel Stunnel vulnerability
A flaw was found in the way stunnel, a socket wrapper which can provide SSL support to ordinary applications, performed (re)initialization of PRNG after fork. When accepting a new connection, the server forks and the child process handles the request. The RANDbytes() function of openssl doesn't reset its state after the fork, but seeds the PRNG with the output of time(NULL). The most important consequence is that servers using EC (ECDSA) or DSA certificates may under certain conditions leak their private key.
Other sources
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.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
stunnelto a version that resolves this vulnerability.Fixed in 5.00 - Compensating control
If you are using stunnel with fork threading and cannot upgrade to stunnel 5.00 yet, mitigate exposure by avoiding the vulnerable forked-child reuse scenario (so children do not share the same PRNG state/entropy pool after fork).
- Operational
For any servers that may have leaked private keys (EC/ECDSA or DSA), rotate/revoke the affected certificates/private keys after upgrading.
Event History
Frequently Asked Questions
What is the severity of CVE-2014-0016?
CVE-2014-0016 is considered a critical severity vulnerability due to improper random number generation after a fork, which can lead to predictable SSL keys.
How do I fix CVE-2014-0016?
To fix CVE-2014-0016, it is recommended to upgrade to a fixed version of stunnel software that has addressed this vulnerability.
Which versions of stunnel are affected by CVE-2014-0016?
CVE-2014-0016 affects stunnel versions up to 4.55 and certain versions from 0.1 to 3.23.
What is the impact of exploiting CVE-2014-0016?
Exploiting CVE-2014-0016 can lead to compromised SSL communications due to predictable encryption keys.
Is there a known exploit for CVE-2014-0016?
There have been reports of exploits leveraging CVE-2014-0016 to compromise SSL connections, making immediate remediation important.