What is CVE-2026-61801?

CVE-2026-61801 is a medium-severity uncontrolled resource consumption vulnerability in github.com/moby/sys/user (go), affecting versions <= 0.4.0. It is fixed in 0.4.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.

How severe is CVE-2026-61801?

CVE-2026-61801 has a CVSS score of 5.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of github.com/moby/sys/user are affected by CVE-2026-61801?

github.com/moby/sys/user (go) versions <= 0.4.0 is affected.

Is there a fix for CVE-2026-61801?

Yes. CVE-2026-61801 is fixed in 0.4.1. Upgrade to this version or later.

Is CVE-2026-61801 exploitable, and should I be worried?

Whether CVE-2026-61801 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2026-61801 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

How do I fix CVE-2026-61801?

Upgrade github.com/moby/sys/user to 0.4.1 or later.

CVE-2026-61801 in github.com/moby/sys/user

Q: How severe is CVE-2026-61801?

CVE-2026-61801 has a CVSS score of 5.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of github.com/moby/sys/user are affected by CVE-2026-61801?

github.com/moby/sys/user (go) versions <= 0.4.0 is affected.

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

Yes. CVE-2026-61801 is fixed in 0.4.1. Upgrade to this version or later.

Q: Is CVE-2026-61801 exploitable, and should I be worried?

Whether CVE-2026-61801 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2026-61801 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2026-61801?

Upgrade github.com/moby/sys/user to 0.4.1 or later.

Summary

github.com/moby/sys/user has a possible DoS via unbounded parsing of user and group database files

A denial-of-service (DoS) vulnerability exists in github.com/moby/sys/user before v0.4.1 when parsing specially crafted user or group database files. An attacker able to supply a malicious /etc/passwd or /etc/group-style file may cause excessive memory consumption, potentially resulting in process termination due to Out Of Memory (OOM) conditions.

This issue is related to containerd [CVE-2026-47262] / GHSA-jpcc-p29g-p8mq, which describes one practical exploitation path through processing untrusted container image content. Applications using github.com/moby/sys/user to parse untrusted user or group database files may be similarly affected.

Workarounds

Avoid parsing attacker-controlled /etc/passwd or /etc/group-style files with affected versions of github.com/moby/sys/user.

Applications that must process untrusted user or group database files should validate and limit accepted input before parsing. Upgrading to v0.4.1 or later is the recommended remediation.

References

containerd CVE-2026-47262 / GHSA-jpcc-p29g-p8mq: https://github.com/containerd/containerd/security/advisories/GHSA-jpcc-p29g-p8mq
Fix in github.com/moby/sys/user: https://github.com/moby/sys/user/commit/210d32ba2bcb4544ee968c7f31249fe59796e60b

Impact

github.com/moby/sys/user versions before v0.4.1 do not place sufficient limits on entries while parsing user and group database files. A specially crafted file may cause excessive memory consumption, potentially leading to process termination due to Out Of Memory (OOM) conditions.

Applications that use github.com/moby/sys/user to parse user-supplied or otherwise untrusted /etc/passwd or /etc/group files may be affected. The severity depends on whether an attacker can influence the contents of files being parsed.

Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service. Typical impact: denial of service.

CVE-2026-61801 has a CVSS score of 5.5 (Medium). The vector is requires local access, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.4.1); upgrading removes the vulnerable code path.

Affected versions

github.com/moby/sys/user (<= 0.4.0)

Security releases

github.com/moby/sys/user → 0.4.1 (go)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

This issue is fixed in github.com/moby/sys/user v0.4.1. Users should upgrade to v0.4.1 or later.

Frequently Asked Questions

What is CVE-2026-61801? CVE-2026-61801 is a medium-severity uncontrolled resource consumption vulnerability in github.com/moby/sys/user (go), affecting versions <= 0.4.0. It is fixed in 0.4.1. Crafted input forces the application to consume excessive CPU, memory, or other resources, degrading or denying service.
How severe is CVE-2026-61801? CVE-2026-61801 has a CVSS score of 5.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of github.com/moby/sys/user are affected by CVE-2026-61801? github.com/moby/sys/user (go) versions <= 0.4.0 is affected.
Is there a fix for CVE-2026-61801? Yes. CVE-2026-61801 is fixed in 0.4.1. Upgrade to this version or later.
Is CVE-2026-61801 exploitable, and should I be worried? Whether CVE-2026-61801 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2026-61801 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2026-61801? Upgrade github.com/moby/sys/user to 0.4.1 or later.