# CVE-2026-39944: Ceph: CephX AES Authentication error

> Attackers with valid STS tokens can tamper with unencrypted AES-CBC fields to gain full administrative access to Ceph RADOS Gateway.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Aug 2026
- **Updated:** 1 Sep 2026
- **Also known as:** BIT-ceph-2026-39944, DEBIAN-CVE-2026-39944, ECHO-81df-cb66-3def, GHSA-j73r-qrgx-jvq2, MINI-3qph-pgr9-fc22, MINI-x459-rwph-mh2j, UBUNTU-CVE-2026-39944

## What is CVE-2026-39944?

CVE-2026-39944 is a high-severity vulnerability in ceph, published on 27 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Ceph is an open-source distributed storage platform providing object, block, and file storage. In versions prior to 20.2.4 and 19.2.6, the RADOS Gateway (RGW) protects STS session tokens with an AES-128-CBC handler that provides no message authentication, allowing an attacker who holds any valid STS token to tamper with it undetected and escalate to full RGW administrative access. Because the ciphertext is unauthenticated, the attacker can perform a CBC bit-flip on the acct_type, perm_type, and is_admin fields of their own token, and a forged is_admin value triggers a global administrative override that bypasses all capability checks. The attack is reachable remotely over the RGW S3 endpoint and is a self-contained modification of a token the attacker already possesses, requiring no encryption oracle and no network observation. It requires only a single valid STS token, which need not carry any elevated privileges, with STS enabled. This issue is fixed in versions 20.2.4 and 19.2.6.

Weakness: CWE-327 (Use of a Broken or Risky Cryptographic Algorithm)

## Which versions are affected by CVE-2026-39944?

1 open source package ship an affected version, including ceph.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ceph` | Bitnami | From 19.0.0 | 19.2.6, 20.2.4 |

## How do I fix CVE-2026-39944?

Upgrade ceph to a fixed version for your release line: 19.2.6 or 20.2.4.

## Is CVE-2026-39944 being exploited?

There is no known exploitation of CVE-2026-39944 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-39944 and fix it if it is affected.

What it is: CVE-2026-39944 is a high-severity vulnerability in ceph, published on 27 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-39944 in the wild and no public exploit code.

Affected packages and fixed versions:
- ceph (Bitnami): affected from 19.0.0; fixed in 19.2.6, 20.2.4

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-2026-39944/ (Markdown: https://insights.sbomify.com/CVE-2026-39944/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-39944
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-39944
- OSV: https://osv.dev/vulnerability/CVE-2026-39944

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-39944/
Summaries are generated and may contain mistakes; the official description above is the record.