CVE-2026-61801 github.com/moby/sys/user has a possible DoS via unbounded parsing of user and group database files
An attacker can cause a denial of service via excessive memory consumption by supplying a crafted user or group database file to the moby/sys/user Go library.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-61801?
CVE-2026-61801 is a medium-severity denial of service vulnerability in moby sys, published on 8 Oct 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
The `github.com/moby/sys/user` package provides Go utilities for parsing and looking up entries in Unix-style user and group database files. Versions before 0.4.1 do not sufficiently limit entries when parsing `/etc/passwd`- or `/etc/group`-style files, allowing an attacker who can supply a specially crafted file to cause excessive memory consumption and potentially terminate the affected process due to an out-of-memory condition. This issue is patched in version 0.4.1. As a workaround, avoid parsing attacker-controlled user or group database files, or validate and limit untrusted input before parsing it.
Weakness: CWE-400
Which versions are affected by CVE-2026-61801?
3 open source packages ship an affected version, including github.com/moby/sys/user.
| Package | Affected | Fixed in |
|---|---|---|
github.com/moby/sys/user Go | All versions | 0.4.1 |
github.com/moby/sys/user Go | All versions | 0.4.1 |
github.com/moby/sys/user Go | All versions | 0.4.1 |
How do I fix CVE-2026-61801?
Upgrade github.com/moby/sys/user to 0.4.1 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-61801 being exploited?
There is no known exploitation of CVE-2026-61801 in the wild and no public exploit code.
Sources
Also known as AZL-107042, AZL-107072, AZL-107099, AZL-107111, AZL-107243, AZL-107261 and 150 more.