# CVE-2026-49952: Discuz! X5.0 Authentication Bypass via dbbak.php Encryption Oracle

> Unauthenticated attackers can bypass authentication to access database backup and restore functions, potentially modifying data or impersonating users.

- **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Jun 2026
- **Updated:** 28 Jul 2026
- **Also known as:** GHSA-mx47-h32c-x878

## What is CVE-2026-49952?

CVE-2026-49952 is a critical authentication bypass vulnerability in Discuz! X5.0, published on 15 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Discuz! X5.0 releases 20260320 through 20260501 contains an authentication bypass vulnerability that allows unauthenticated remote attackers to gain unauthorized access to database backup and restore functionality by exploiting a shared cryptographic key between UCenter integration and the database backup API exposed by dbbak.php. Attackers can inject a crafted payload through the username parameter during login to abuse the encryption oracle in logging_ctl::logging_more(), obtain a legitimately signed token, and use it to bypass authorization for database export and import operations, with the additional ability to trigger a race condition to impersonate arbitrary users.

Weakness: CWE-323 (Reusing a Nonce, Key Pair in Encryption)

## Which versions are affected by CVE-2026-49952?


## How do I fix CVE-2026-49952?

No fix has been published for CVE-2026-49952 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-49952 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-49952 exists.

Public exploit code:

- Chaining Security Bugs in Discuz! X5.0: from Race Condition to Pre-Auth RCE (github_poc): https://github.com/passwa11/CVE-2026-49952
- Discuz! X5.0 Authentication Bypass Exploit Framework (CVE-2026-49952) - Critical vulnerability allowing unauthenticated database backup access via UC_KEY encryption oracle token reuse. CVSS 9.1. Full-featured tool with version detection, multi-payload attacks, interactive shell, and automated exploitation. Authorized testing only. (github_poc): https://github.com/CerberusMrXi/Discuz-X5.0-Authentication-Bypass-Exploit-Framework
- Discuz! X5.0 - Authentication Bypass (exploitdb)
- Discuz! X5.0 - Authentication Bypass (nuclei): http/cves/2026/CVE-2026-49952.yaml

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-49952 and fix it if it is affected.

What it is: CVE-2026-49952 is a critical authentication bypass vulnerability in Discuz! X5.0, published on 15 Jun 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-2026-49952 exists.

Affected product: Discuz! X5.0. 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-2026-49952/ (Markdown: https://insights.sbomify.com/CVE-2026-49952/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-49952
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-49952
- OSV: https://osv.dev/vulnerability/CVE-2026-49952

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-49952/
Summaries are generated and may contain mistakes; the official description above is the record.