# CVE-2026-70452: rsync 3.1.0 < 3.5.0 Access Control Bypass via DNS Resolution Failure

> Remote attackers can bypass hostname-based access controls in rsync by triggering DNS failures, gaining unauthorized access to restricted file trees.

- **Severity:** Critical 9.1 (`CVSS:4.0/AV:N/AC:H/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:** Yes
- **Published:** 13 Aug 2026
- **Updated:** 14 Aug 2026
- **Also known as:** ALPINE-CVE-2026-70452, AZL-95795, BELL-CVE-2026-70452, DEBIAN-CVE-2026-70452, ECHO-bdc4-0ff5-9a3d, GHSA-6692-28cx-wpqq, ROOT-OS-DEBIAN-11-CVE-2026-70452, UBUNTU-CVE-2026-70452

## What is CVE-2026-70452?

CVE-2026-70452 is a critical authentication bypass vulnerability in RsyncProject rsync, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

rsync 3.1.0 before 3.5.0 contains an access control bypass vulnerability that allows remote attackers to circumvent hosts deny rules by inducing DNS resolution failures during hostname-based access control evaluation. When a DNS lookup for a hostname-based deny rule fails, the daemon skips the rule rather than defaulting to a deny decision, enabling attackers who can trigger DNS failures to bypass module-level IP access controls and gain unauthorized access to restricted module file trees.

Weakness: CWE-863 (Incorrect Authorization), CWE-636 (Not Failing Securely)

## Which versions are affected by CVE-2026-70452?


## How do I fix CVE-2026-70452?

Upgrade to a fixed version.

## Is CVE-2026-70452 being exploited?

There is no known exploitation of CVE-2026-70452 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-70452 and fix it if it is affected.

What it is: CVE-2026-70452 is a critical authentication bypass vulnerability in RsyncProject rsync, published on 13 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-70452 in the wild and no public exploit code.

Affected product: RsyncProject rsync. 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-2026-70452/ (Markdown: https://insights.sbomify.com/CVE-2026-70452/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-70452
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-70452
- OSV: https://osv.dev/vulnerability/CVE-2026-70452

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-70452/
Summaries are generated and may contain mistakes; the official description above is the record.