# CVE-2026-70453: rsync < 3.5.0 Algorithmic Complexity DoS via hash_search()

> Remote attackers can cause denial of service in rsync by sending crafted file lists that trigger quadratic-time hash lookups, exhausting CPU resources.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/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-2026-70453, AZL-95855, BELL-CVE-2026-70453, DEBIAN-CVE-2026-70453, ECHO-079f-04d3-1628, GHSA-8x5r-mjx8-83hv, ROOT-OS-DEBIAN-11-CVE-2026-70453, UBUNTU-CVE-2026-70453

## What is CVE-2026-70453?

CVE-2026-70453 is a high-severity denial of service 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 before 3.5.0 contains an algorithmic complexity vulnerability in the hash_search() function that allows a remote attacker to cause a denial of service by delivering a carefully constructed file list. A sender can exploit the quadratic-time worst-case behavior in hash lookups to exhaust receiver CPU resources with a modest number of crafted entries, causing a sustained denial of service.

Weakness: CWE-407 (Inefficient Algorithmic Complexity)

## Which versions are affected by CVE-2026-70453?


## How do I fix CVE-2026-70453?

Upgrade to a fixed version.

## Is CVE-2026-70453 being exploited?

There is no known exploitation of CVE-2026-70453 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-70453 and fix it if it is affected.

What it is: CVE-2026-70453 is a high-severity denial of service 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-2026-70453 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-2026-70453/ (Markdown: https://insights.sbomify.com/CVE-2026-70453/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-70453
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-70453
- OSV: https://osv.dev/vulnerability/CVE-2026-70453

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-70453/
Summaries are generated and may contain mistakes; the official description above is the record.