diff --git a/crates/openssl-src/RUSTSEC-0000-0000.md b/crates/openssl-src/RUSTSEC-0000-0000.md
new file mode 100644
index 0000000..c30600d
--- /dev/null
+++ b/crates/openssl-src/RUSTSEC-0000-0000.md
@@ -0,0 +1,35 @@
+```toml
+[advisory]
+id = "RUSTSEC-0000-0000"
+package = "openssl-src"
+aliases = ["CVE-2021-4044"]
+categories = ["denial-of-service"]
+date = "2021-12-14"
+url = "https://www.openssl.org/news/secadv/20211214.txt"
+
+[versions]
+patched = [">= 300.0.4"]
+unaffected = ["< 300.0.0"]
+```
+
+# Invalid handling of `X509_verify_cert()` internal errors in libssl
+
+Internally libssl in OpenSSL calls `X509_verify_cert()` on the client side to
+verify a certificate supplied by a server. That function may return a negative
+return value to indicate an internal error (for example out of memory). Such a
+negative return value is mishandled by OpenSSL and will cause an IO function
+(such as `SSL_connect()` or `SSL_do_handshake()`) to not indicate success and a
+subsequent call to `SSL_get_error()` to return the value
+`SSL_ERROR_WANT_RETRY_VERIFY`. This return value is only supposed to be returned
+by OpenSSL if the application has previously called
+`SSL_CTX_set_cert_verify_callback()`. Since most applications do not do this the
+`SSL_ERROR_WANT_RETRY_VERIFY` return value from `SSL_get_error()` will be totally
+unexpected and applications may not behave correctly as a result. The exact
+behaviour will depend on the application but it could result in crashes,
+infinite loops or other similar incorrect responses.
+
+This issue is made more serious in combination with a separate bug in OpenSSL
+3.0 that will cause `X509_verify_cert()` to indicate an internal error when
+processing a certificate chain. This will occur where a certificate does not
+include the Subject Alternative Name extension but where a Certificate Authority
+has enforced name constraints. This issue can occur even with valid chains.