CVE-2025-4437
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedThere's a vulnerability in the CRI-O application where when container is launched with securityContext.runAsUser specifying a non-existent user, CRI-O attempts to create the user, reading the container's entire /etc/passwd file into memory. If this file is excessively large, it can cause the a high memory consumption leading applications to be killed due to out-of-memory. As a result a denial-of-service can be achieved, possibly disrupting other pods and services running in the same host.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceIn CRI-O, when a container is launched with securityContext.runAsUser specifying a non-existent user, CRI-O attempts to create that user by reading the entire /etc/passwd file into memory. If /etc/passwd is excessively large, this causes high memory consumption leading to OOM kills of applications, resulting in denial-of-service that can affect other pods on the same host.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- Low
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:N/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify CRI-O versionRun 'crio --version' or check the package version installed on the node (e.g., 'rpm -q cri-o' or 'dpkg -l cri-o')Affected if The installed version is lower than the patched version (check vendor advisories for the fixed release)
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Check /etc/passwd file sizeRun 'ls -lh /etc/passwd' and 'wc -l /etc/passwd' to see the file size and line countAffected if /etc/passwd is unusually large (thousands of lines or tens of MB) which would amplify memory consumption when the flaw triggers
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Inspect pods for non-existent runAsUserRun 'kubectl get pods --all-namespaces -o jsonpath={.items[*].spec.securityContext.runAsUser}' to list all numeric UIDs specified in securityContext, then verify each UID exists with 'getent passwd <uid>'Affected if Any pod specifies a runAsUser UID that does not exist in /etc/passwd, which triggers the vulnerable code path
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Check for containers with securityContext.runAsUser setReview pod specs: 'kubectl get pods --all-namespaces -o yaml | grep -A2 runAsUser' to identify pods explicitly setting runAsUserAffected if Containers are using runAsUser with arbitrary numeric UIDs rather than documented system users
You are affected if CRI-O is running and any container on your cluster uses securityContext.runAsUser with a non-existent user ID, especially on nodes with large /etc/passwd files.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataUpdate CRI-O to the patched version once available. In the meantime, ensure containers only specify existing users in securityContext.runAsUser and consider monitoring memory usage on nodes.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA3.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-4437 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-4437 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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