Is CVE-2026-61801 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-61801 being exploited in the wild.

How severe is CVE-2026-61801?

Medium severity, with a CVSS score of 5.5, published 8 October 2026.

Which products and versions are affected?

github.com/moby/sys/user (Go) <= 0.4.0, SEMVER:introduced=0,fixed=0.4.1; Moby Sys/User before v0.4.1.

How is CVE-2026-61801 attacked?

It is attacked with local access.

Am I affected by CVE-2026-61801?

Check whether you run github.com/moby/sys/user (Go) or Moby Sys/User at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-61801: moby/sys/user denial of service via unbounded parsing

Q: Is there a fix for CVE-2026-61801?

Yes. github.com/moby/sys/user (Go): upgrade to 0.4.1 or later. Until then: Avoid parsing user-supplied or untrusted passwd or group files with affected versions. If processing untrusted input is necessary, validate and limit accepted entries before parsing with moby/sys/user. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: How is CVE-2026-61801 attacked?

It is attacked with local access.

Q: Am I affected by CVE-2026-61801?

Check whether you run github.com/moby/sys/user (Go) or Moby Sys/User at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-61801 · Severity: medium · CVSS 5.5 · Published 2026-10-08

A Go library used by container runtimes to parse user and group database files can be forced to consume excessive memory when processing specially crafted files. An attacker who can supply a malicious passwd or group file could cause the application to run out of memory and crash, disrupting service availability.

Vendors: Go, Moby.

Quick answers

Is CVE-2026-61801 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-61801 being exploited in the wild.
How severe is CVE-2026-61801?: Medium severity, with a CVSS score of 5.5, published 8 October 2026.
Which products and versions are affected?: github.com/moby/sys/user (Go) <= 0.4.0, SEMVER:introduced=0,fixed=0.4.1; Moby Sys/User before v0.4.1.
Is there a fix for CVE-2026-61801?: Yes. github.com/moby/sys/user (Go): upgrade to 0.4.1 or later. Until then: Avoid parsing user-supplied or untrusted passwd or group files with affected versions. If processing untrusted input is necessary, validate and limit accepted entries before parsing with moby/sys/user. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-61801 attacked?: It is attacked with local access.
Am I affected by CVE-2026-61801?: Check whether you run github.com/moby/sys/user (Go) or Moby Sys/User at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

github.com/moby/sys/user (Go): upgrade to 0.4.1 or later
```
go get github.com/moby/sys/user@v0.4.1
```

Avoid parsing user-supplied or untrusted passwd or group files with affected versions. If processing untrusted input is necessary, validate and limit accepted entries before parsing with moby/sys/user.

Technical details

The moby/sys/user library fails to enforce limits on entries when parsing /etc/passwd or /etc/group-style files, allowing a specially crafted file to trigger unbounded memory allocation and exhaustion. The vulnerability requires an attacker to be able to control or supply the contents of the parsed file. A fix enforcing proper bounds checking was introduced in v0.4.1.

Affected products

moby sys/user before v0.4.1

Identifiers

CVE-2026-61801
GHSA-mjcv-p78q-w5fw
GO-2026-6686

Timeline

2026-10-08: disclosed

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