{"id":"UBUNTU-CVE-2026-53939","details":"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).","modified":"2026-09-16T14:01:43.025149216Z","published":"2026-09-09T00:17:00Z","upstream":["CVE-2026-53939"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-53939"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-53939"}],"affected":[{"package":{"name":"cjose","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/cjose?arch=source&distro=esm-apps%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.4.1-3ubuntu1","0.5.1+dfsg1-1","0.5.1+dfsg1-2","0.5.1+dfsg1-2build1","0.6.0+dfsg1-1","0.6.0+dfsg1-1ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"libcjose0","binary_version":"0.6.0+dfsg1-1ubuntu0.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-53939.json"}},{"package":{"name":"cjose","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/cjose?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6.1+dfsg1-1","0.6.1+dfsg1-1ubuntu0.1"],"ecosystem_specific":{"binaries":[{"binary_name":"libcjose0","binary_version":"0.6.1+dfsg1-1ubuntu0.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-53939.json"}},{"package":{"name":"cjose","ecosystem":"Ubuntu:22.04:LTS","purl":"pkg:deb/ubuntu/cjose?arch=source&distro=jammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6.1+dfsg1-1","0.6.1+dfsg1-3","0.6.1+dfsg1-3ubuntu1","0.6.1+dfsg1-3ubuntu1.1"],"ecosystem_specific":{"binaries":[{"binary_name":"libcjose0","binary_version":"0.6.1+dfsg1-3ubuntu1.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-53939.json"}},{"package":{"name":"cjose","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/cjose?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6.2.2-1","0.6.2.2-1build1","0.6.2.2-1build2","0.6.2.2-1build3"],"ecosystem_specific":{"binaries":[{"binary_name":"libcjose0","binary_version":"0.6.2.2-1build3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-53939.json"}},{"package":{"name":"cjose","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/cjose?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.6.2.3-1","0.6.2.4-1"],"ecosystem_specific":{"binaries":[{"binary_version":"0.6.2.4-1","binary_name":"libcjose0"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-53939.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"},{"type":"Ubuntu","score":"medium"}]}