Resource leakage when decoding certificates and keys

Vulnerability

CVE-2022-1473 is a memory leak and performance degradation vulnerability in the OPENSSL_LH_flush() function of OpenSSL 3.0.0, 3.0.1, and 3.0.2. The function is responsible for emptying a hash table, but a bug prevents the reuse of memory occupied by removed entries. This function is used internally when decoding certificates or keys. Consequently, any long-lived process that periodically decodes certificates or keys (such as TLS clients or servers with client certificate authentication enabled) will see its memory usage grow without bounds and will experience increasingly slow hash table traversal, potentially leading to termination by the operating system. Older OpenSSL releases (1.x.y) are not affected [1][2].

Exploitation

An attacker does not need special network position or authentication; the vulnerability is triggered by normal certificate or key decoding operations. For a server that accepts client certificate authentication, an attacker can repeatedly present certificates for decoding, causing the server's memory to expand indefinitely over time and its performance to degrade. The attacker only needs to maintain a long-lived session or series of connections that cause repeated certificate decoding. No user interaction or race condition is required [1][2].

Impact

Successful exploitation results in a denial of service (DoS) through unbounded memory consumption and increased processing time. The availability impact is High, while confidentiality and integrity are not affected. The process (such as a TLS server) may be terminated by the operating system when it runs out of memory [1]. The CVSS score is 7.5 (HIGH) with vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H [4].

Mitigation

The vulnerability is fixed in OpenSSL 3.0.3 (released May 3, 2022). Users of OpenSSL 3.0.0, 3.0.1, or 3.0.2 should upgrade immediately. For the Rust ecosystem, the patched version of the openssl-src crate is 300.0.6 (and later) for the 3.0 stream; the 1.1.1/111 stream is not affected [2][3][4]. No workaround is available for unpatched versions. The issue is not listed in CISA's Known Exploited Vulnerabilities (KEV) catalog as of this writing.