https://github.com/OpenIDC/cjose/security/advisories/GHSA-f6wf-pqg3-6wqq reports:
OpenIDC/cjose is a C library implementing the Javascript
Object Signing and Encryption (JOSE). In versions 0.6.1
through 0.6.2.5, when cjose encrypts a JWE using an
AES-CBC-HMAC content-encryption algorithm (`A128CBC-HS256`,
`A192CBC-HS384`, or `A256CBC-HS512`) together with any
key-management algorithm that generates a fresh
content-encryption key (CEK), the CEK is all zero bytes
instead of being randomly generated. The resulting JWE is
therefore encrypted and authenticated under a fixed,
publicly known key, so anyone who obtains the JWE can
recover the plaintext and forge or modify the content. This
is fixed in version 0.6.2.6 by
`_cjose_jwe_set_cek_aes_cbc()` generating the CEK from
`RAND_bytes`. A regression test asserts that the
`encrypted_key` differs across two encryptions for each
AES-CBC-HMAC variant. Until upgrading, for data encrypted
with cjose, three options are available. Use an AES-GCM
`enc` (`A128GCM` / `A192GCM` / `A256GCM`) instead of an
AES-CBC-HMAC `enc`, use `alg=dir` with a caller-supplied
CEK, or avoid using cjose for JWE encryption with the
affected algorithm pair. These are mitigations for new
ciphertexts only; data already encrypted under the zero key
remains compromised and should be
re-encrypted (and any secrets it contained rotated).