# CVE-2026-16599: Denial of Service in GNU wget

> A malicious FTP server can cause GNU wget to hang by sending a crafted OPIE challenge with a high sequence number, leading to excessive CPU usage.

- **Severity:** Medium 5.1 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 25 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** BELL-CVE-2026-16599, DEBIAN-CVE-2026-16599, ECHO-bd25-6c0f-4704, GHSA-48r3-mr49-jp8x, MGASA-2026-0386, OESA-2026-3766, OESA-2026-3767, OESA-2026-3768, OESA-2026-3769, OESA-2026-3910, SUSE-SU-2026:23455-1, SUSE-SU-2026:23520-1, SUSE-SU-2026:23975-1, SUSE-SU-2026:23991-1, SUSE-SU-2026:4049-1, SUSE-SU-2026:4053-1, SUSE-SU-2026:4074-1, UBUNTU-CVE-2026-16599, openSUSE-SU-2026:11646-1, openSUSE-SU-2026:22011-1

## What is CVE-2026-16599?

CVE-2026-16599 is a medium-severity denial of service vulnerability in GNU wget, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

GNU wget is vulnerable to denial of service in its FTP OPIE/S-KEY authentication functionality. The server-supplied sequence number from the FTP challenge line is used as an iteration count for an MD5 key-derivation loop without any upper bound validation. A malicious FTP server or a network attacker positioned to intercept FTP traffic can send a crafted OPIE challenge with a sequence number near INT_MAX, causing wget to perform up to approximately 2.1 billion MD5 computations and suspend for some time. The --timeout option does not mitigate this because it applies only to network I/O, not CPU computation.

This issue was fixed in commit e9697d98e7249b0f68a6be040a4f3dcc5bc101fa

Weakness: CWE-606 (Unchecked Input for Loop Condition)

## Which versions are affected by CVE-2026-16599?


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `wget` | SUSE:Linux Enterprise Micro 5.5 | All versions | 1.20.3-150000.3.40.1 |
| `wget` | SUSE:Linux Enterprise Module for Basesystem 15 SP7 | All versions | 1.24.5-150700.3.12.1 |
| `wget` | SUSE:Linux Enterprise Server 16.0 | All versions | 1.25.0-160000.4.1 |
| `wget` | SUSE:Linux Enterprise Server LTSS Extended Security 12 SP5 | All versions | 1.14-21.31.1 |
| `wget` | SUSE:Linux Enterprise Server for SAP applications 16.0 | All versions | 1.25.0-160000.4.1 |
| `wget` | SUSE:Linux Micro 6.0 | All versions | 1.24.5-5.1 |
| `wget` | SUSE:Linux Micro 6.1 | All versions | 1.24.5-slfo.1.1_6.1 |
| `wget` | SUSE:Linux Micro 6.2 | All versions | 1.25.0-160000.4.1 |
| `wget` | openSUSE:Leap 16.0 | All versions | 1.25.0-160000.4.1 |
| `wget` | openSUSE:Tumbleweed | All versions | 1.25.0-7.1 |

## How do I fix CVE-2026-16599?

Apply the vendor's patch.

## Is CVE-2026-16599 being exploited?

There is no known exploitation of CVE-2026-16599 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-16599 and fix it if it is affected.

What it is: CVE-2026-16599 is a medium-severity denial of service vulnerability in GNU wget, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-16599 in the wild and no public exploit code.

Affected product: GNU wget. 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-2026-16599/ (Markdown: https://insights.sbomify.com/CVE-2026-16599/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-16599
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-16599
- OSV: https://osv.dev/vulnerability/CVE-2026-16599

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-16599/
Summaries are generated and may contain mistakes; the official description above is the record.