# CVE-2026-70457: rsync 3.2.3 < 3.5.0 Out-of-Bounds Write via parse_size_arg()

> An out-of-bounds write in rsync allows attackers to corrupt memory, potentially leading to code execution or denial of service.

- **Severity:** High 8.3 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:L/VA:H/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-2026-70457, AZL-95846, BELL-CVE-2026-70457, DEBIAN-CVE-2026-70457, ECHO-112e-6676-e997, GHSA-pg7g-xqmr-xpfh, ROOT-OS-DEBIAN-11-CVE-2026-70457, UBUNTU-CVE-2026-70457

## What is CVE-2026-70457?

CVE-2026-70457 is a high-severity memory corruption 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 3.2.3 before 3.5.0 contains an out-of-bounds write in parse_size_arg() where the return value of snprintf() is used directly as an index into a .bss-segment array without bounds checking. When snprintf truncates the formatted size string, the return value equals the number of characters that would have been written including the truncated portion, and this value may exceed the array length. The subsequent indexed write targets memory outside the intended array bounds, corrupting .bss memory.

Weakness: CWE-787 (Out-of-bounds Write), CWE-131 (Incorrect Calculation of Buffer Size)

## Which versions are affected by CVE-2026-70457?

It affects 1 product.


Products: Samba Rsync.

## How do I fix CVE-2026-70457?

Upgrade to a fixed version.

## Is CVE-2026-70457 being exploited?

There is no known exploitation of CVE-2026-70457 in the wild and no public exploit code.

## Other vulnerabilities in RsyncProject rsync

- [CVE-2017-15994](https://insights.sbomify.com/CVE-2017-15994/): Security feature bypass in n/a (critical 9.8)
- [CVE-2026-53791](https://insights.sbomify.com/CVE-2026-53791/): rsync < 3.5.0 Daemon IP Spoofing via PROXY Protocol Header (critical 9.1)
- [CVE-2026-70461](https://insights.sbomify.com/CVE-2026-70461/): rsync 3.2.5 < 3.5.0 Heap Out-of-Bounds Write via files-from Entry (high 8.8)
- [CVE-2026-70455](https://insights.sbomify.com/CVE-2026-70455/): rsync 3.4.2 < 3.5.0 DoS via --zt Zstandard Compression Thread Exhaustion (high 8.7)
- [CVE-2026-70463](https://insights.sbomify.com/CVE-2026-70463/): rsync 3.1.0 < 3.5.0 Authorization Bypass via auth users Directive Parsing (high 8.6)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-70457 and fix it if it is affected.

What it is: CVE-2026-70457 is a high-severity memory corruption 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-2026-70457 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-2026-70457/ (Markdown: https://insights.sbomify.com/CVE-2026-70457/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-70457
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-70457
- OSV: https://osv.dev/vulnerability/CVE-2026-70457

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-70457/
Summaries are generated and may contain mistakes; the official description above is the record.