CVE-2015-1791 in Secure Backup
Summary
by MITRE
Race condition in the ssl3_get_new_session_ticket function in ssl/s3_clnt.c in OpenSSL before 0.9.8zg, 1.0.0 before 1.0.0s, 1.0.1 before 1.0.1n, and 1.0.2 before 1.0.2b, when used for a multi-threaded client, allows remote attackers to cause a denial of service (double free and application crash) or possibly have unspecified other impact by providing a NewSessionTicket during an attempt to reuse a ticket that had been obtained earlier.
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Analysis
by VulDB Data Team • 11/01/2022
The vulnerability described in CVE-2015-1791 represents a critical race condition affecting OpenSSL implementations across multiple version branches including 0.9.8, 1.0.0, 1.0.1, and 1.0.2 series. This flaw specifically targets the ssl3_get_new_session_ticket function located in ssl/s3_clnt.c, where the improper handling of session ticket reuse creates exploitable conditions in multi-threaded client environments. The vulnerability manifests when a client attempts to reuse a previously obtained session ticket while simultaneously receiving a NewSessionTicket message from the server, creating a timing window where memory management operations become inconsistent.
The technical exploitation of this race condition occurs through a carefully orchestrated sequence where remote attackers can manipulate the timing of session ticket exchanges to trigger memory corruption. When a client processes a NewSessionTicket message while concurrently attempting to reuse an existing ticket, the underlying OpenSSL code fails to properly synchronize access to shared session ticket structures. This lack of proper thread synchronization results in double free operations where the same memory block gets freed twice, leading to heap corruption that can cause application crashes or potentially more severe memory corruption issues. The vulnerability is particularly dangerous in multi-threaded environments where multiple concurrent connections might be processed simultaneously, amplifying the potential impact of the race condition.
From an operational perspective, this vulnerability presents significant risks to applications relying on OpenSSL for secure communications, particularly those handling high volumes of concurrent connections. The denial of service impact can effectively render services unavailable to legitimate users, while the potential for unspecified other impacts suggests possibilities of information disclosure or privilege escalation depending on the specific implementation and execution environment. Network infrastructure components, web servers, and applications using OpenSSL for TLS connections become vulnerable to this attack vector, with the risk being proportional to the number of concurrent connections and the frequency of session ticket reuse operations. The vulnerability's exploitation does not require authentication or specialized privileges, making it particularly dangerous in environments where attackers can directly interact with vulnerable services.
Mitigation strategies for CVE-2015-1791 primarily focus on upgrading to patched versions of OpenSSL where the race condition has been resolved through proper thread synchronization mechanisms and memory management improvements. System administrators should prioritize updating all affected OpenSSL installations across their infrastructure, with particular attention to multi-threaded applications that frequently reuse session tickets. Additional protective measures include implementing connection rate limiting, monitoring for unusual session ticket patterns, and configuring applications to minimize concurrent session ticket operations. Organizations should also consider disabling session ticket reuse functionality temporarily if immediate patching is not feasible, though this approach may impact performance and connection efficiency. The vulnerability aligns with CWE-362, which describes race conditions in concurrent programming, and represents a typical example of how improper synchronization can lead to memory corruption issues. From an ATT&CK framework perspective, this vulnerability could be categorized under privilege escalation and denial of service techniques, as it allows attackers to disrupt service availability and potentially compromise system stability through memory corruption attacks.