# CVE-2026-53939: OpenIDC/cjose uses all-zero Content Encryption Key for AES-CBC-HMAC JWE encryption > Attackers can decrypt and forge JWE tokens because the library uses an all-zero key for AES-CBC-HMAC encryption, compromising confidentiality and integrity. - **Severity:** Critical 9.1 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 8 Sep 2026 - **Updated:** 9 Sep 2026 - **Also known as:** ALSA-2026:80605, ALSA-2026:92145, ALSA-2026:92157, AZL-101096, CLSA-2026-1792632603, DEBIAN-CVE-2026-53939, GHSA-f6wf-pqg3-6wqq, RHSA-2026:80605, RHSA-2026:83224, RLSA-2026:80605, RLSA-2026:92157, UBUNTU-CVE-2026-53939 ## What is CVE-2026-53939? CVE-2026-53939 is a critical vulnerability in OpenIDC cjose, published on 8 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description 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). Weakness: CWE-330 (Use of Insufficiently Random Values), CWE-321 (Use of Hard-coded Cryptographic Key) ## Which versions are affected by CVE-2026-53939? | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `cjose` | AlmaLinux:10 | All versions | 0.6.2.2-7.el10_2.2 | | `cjose-devel` | AlmaLinux:10 | All versions | 0.6.2.2-7.el10_2.2 | | `cjose` | AlmaLinux:8 | All versions | 0.6.1-6.module_el8.10.0+4330+15616d81 | | `cjose-devel` | AlmaLinux:8 | All versions | 0.6.1-6.module_el8.10.0+4330+15616d81 | | `mod_auth_openidc` | AlmaLinux:8 | All versions | 2.4.9.4-9.module_el8.10.0+4297+63ae3533 | | `cjose` | AlmaLinux:9 | All versions | 0.6.1-17.el9_8.2 | | `cjose-devel` | AlmaLinux:9 | All versions | 0.6.1-17.el9_8.2 | | `cjose` | Red Hat:enterprise_linux:10.2 | All versions | 0:0.6.2.2-7.el10_2.2 | | `cjose-debuginfo` | Red Hat:enterprise_linux:10.2 | All versions | 0:0.6.2.2-7.el10_2.2 | | `cjose-debugsource` | Red Hat:enterprise_linux:10.2 | All versions | 0:0.6.2.2-7.el10_2.2 | | `cjose-devel` | Red Hat:enterprise_linux:10.2 | All versions | 0:0.6.2.2-7.el10_2.2 | | `cjose` | Red Hat:enterprise_linux_eus:10.0 | All versions | 0:0.6.2.2-7.el10_0.2 | | `cjose-debuginfo` | Red Hat:enterprise_linux_eus:10.0 | All versions | 0:0.6.2.2-7.el10_0.2 | | `cjose-debugsource` | Red Hat:enterprise_linux_eus:10.0 | All versions | 0:0.6.2.2-7.el10_0.2 | | `cjose-devel` | Red Hat:enterprise_linux_eus:10.0 | All versions | 0:0.6.2.2-7.el10_0.2 | | `cjose` | Rocky Linux:10 | All versions | 0:0.6.2.2-7.el10_2.2 | | `mod_auth_openidc` | Rocky Linux:8 | All versions | 0:2.4.9.4-9.module+el8.10.0+40373+8a3f15d2 | ## How do I fix CVE-2026-53939? Upgrade to a fixed version. ## Is CVE-2026-53939 being exploited? It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53939 exists. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-53939 and fix it if it is affected. What it is: CVE-2026-53939 is a critical vulnerability in OpenIDC cjose, published on 8 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-53939 exists. Affected product: OpenIDC cjose. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-53939/ (Markdown: https://insights.sbomify.com/CVE-2026-53939/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-53939 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-53939 - OSV: https://osv.dev/vulnerability/CVE-2026-53939 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-53939/ Summaries are generated and may contain mistakes; the official description above is the record.