FreeBSDOperating system
CVE-2026-2261
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 · uneditedDue to a programming error, blocklistd leaks a socket descriptor for each adverse event report it receives. Once a certain number of leaked sockets is reached, blocklistd becomes unable to run the helper script: a child process is forked, but this child dereferences a null pointer and crashes before it is able to exec the helper. At this point, blocklistd still records adverse events but is unable to block new addresses or unblock addresses whose database entries have expired. Once a second, much higher number of leaked sockets is reached, blocklistd becomes unable to receive new adverse event reports. An attacker may take advantage of this by triggering a large number of adverse events from sacrificial IP addresses to effectively disable blocklistd before launching an attack. Even in the absence of attacks or probes by would-be attackers, adverse events will occur regularly in the course of normal operations, and blocklistd will gradually run out file descriptors and become ineffective. The accumulation of open sockets may have knock-on effects on other parts of the system, resulting in a general slowdown until blocklistd is restarted.
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 · high confidenceblocklistd leaks socket descriptors for each adverse event report due to a programming error. At a threshold number of leaked sockets, the helper script fork fails with a null pointer dereference, preventing new address blocks; at a higher threshold, the service stops receiving events entirely. An attacker can trigger many adverse events from sacrificial IPs to disable the blocking service before attacking.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
FreeBSDOperating system
= 15.0CVSS 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
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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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Verify FreeBSD version is 15.0Run 'uname -r' or check /etc/os-release to confirm the installed FreeBSD versionAffected if The system is running FreeBSD 15.0 exactly (version matching = 15.0)
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Confirm blocklistd service is installedCheck for the presence of blocklistd binary (typically in /usr/sbin/blocklistd) or check if the package is installed via pkg infoAffected if blocklistd is installed on the system
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Check if blocklistd is enabled and runningUse 'service blocklistd status' or check for the blocklistd process with 'ps aux | grep blocklistd'Affected if blocklistd daemon is actively running
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Inspect system logs for blocklistd errorsReview /var/log/messages or use 'dmesg' for error messages containing 'blocklistd', 'null pointer', or 'fork failed'Affected if Logs show fork failures or null pointer dereference errors from blocklistd
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Check for socket descriptor exhaustion symptomsMonitor open file descriptors for blocklistd process using 'procstat -f <pid>' or check system-wide descriptor usage with 'sysctl kern.maxfiles'Affected if blocklistd is hitting descriptor limits or failing to accept new connections
A system is affected if it runs FreeBSD 15.0 with blocklistd enabled and running, and exhibits symptoms of socket descriptor exhaustion or service failure.
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 dataFix the socket descriptor leak by ensuring sockets are properly closed after each adverse event report; implement resource limits and monitoring to detect descriptor exhaustion before service failure.
Fix this in FreeBSD
Scoped from the published advisory
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2026-2261 — 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-2026-2261 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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- Version or environment caveats, and links to real fixes
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