⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● High · CVSS 7.9 ⚠ ACTIVELY EXPLOITED — CISA KEV

How to Fix CVE-2023-0266: Use-After-Free in Linux Kernel

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 7.9 - High
Actively exploited?Yes, listed in CISA KEV (added 2023-03-30)
Affected4.14 < 56b88b50565cd8b946a2d00b0c83927b7ebb055e
Fixed inSee vendor advisory
Type (CWE)CWE-416: Use After Free
Patch immediately. CISA's KEV listing means active exploitation is confirmed. Federal agencies must remediate by 2023-04-20.

What is CVE-2023-0266?

CVE-2023-0266 is an use-after-free bug in Linux Kernel. A reference to freed memory is dereferenced later in the program, allowing an attacker who controls the reallocated content to hijack execution. Vendor description: A use after free vulnerability exists in the ALSA PCM package in the Linux Kernel. SNDRV_CTL_IOCTL_ELEM_{READ|WRITE}32 is missing locks that can be used in a use-after-free that can result in a priviledge escalation to gain ring0 access from the system user.

Why this CVE matters

Use-after-free vulnerabilities in a network or media-parsing path tend to draw immediate exploit development effort. The bug class is well understood, and public toolkits exist that adapt quickly to newly disclosed cases.

For deployments of Linux Kernel that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Confirmed in-the-wild exploitation makes that assumption mandatory, not cautious. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Run uname -r to read the kernel release. Compare against the affected ranges; on distro kernels, also check the package version with dpkg -l linux-image-$(uname -r) or rpm -q kernel.

How to fix CVE-2023-0266

  1. Read the vendor advisory in full: https://github.com/torvalds/linux/commit/becf9e5d553c2389d857a3c178ce80fdb34a02e1
  2. Upgrade Linux Kernel to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

Apply the Microsoft security update


# The exact KB number is listed in the Microsoft advisory: https://github.com/torvalds/linux/commit/becf9e5d553c2389d857a3c178ce80fdb34a02e1
# Confirm the patch is missing on this host
Get-Hotfix -Id <KB-from-advisory> -ErrorAction SilentlyContinue

# Install the rollup that ships the fix
Install-Module PSWindowsUpdate -Force -SkipPublisherCheck
Import-Module PSWindowsUpdate
Get-WindowsUpdate -KBArticleID <KB-from-advisory> -AcceptAll -Install -AutoReboot

# Verify the patch is now present
Get-Hotfix -Id <KB-from-advisory>


# Inventory missing patches across a Windows fleet via Ansible (winrm)
ansible windows -m win_updates -a "category_names=SecurityUpdates state=installed"

Verify the fix landed


# 1. Confirm the running version matches the fixed-in version from the advisory:
#    https://github.com/torvalds/linux/commit/becf9e5d553c2389d857a3c178ce80fdb34a02e1
#    Use the platform-specific version probe above.

# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag CVE-2023-0266 on the patched target.

# 3. Inspect recent service / kernel logs for crash loops or rollback events.
journalctl -u <service> --since "10 minutes ago"
dmesg --since "10 minutes ago"

If you cannot patch immediately

Block network reachability to the vulnerable service from untrusted networks and apply the patched build. Memory-corruption bugs cannot be reliably mitigated at the network layer; the patch is the fix.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for repeated service restarts, crash logs from the affected daemon, and core files generated around the time of any anomalous traffic. A memory-corruption flaw used for exploitation often leaves a trail of failed attempts before the successful one. Because Linux Kernel sits on CISA's Known Exploited Vulnerabilities catalog for this CVE, defenders should also pull the IOC list from the vendor advisory and from CISA's analysis if one was published.

Frequently asked questions

Is CVE-2023-0266 being exploited in the wild?

Yes. CISA added CVE-2023-0266 to the Known Exploited Vulnerabilities catalog, which means active exploitation has been confirmed by federal observation or credible vendor reporting.

Will a WAF or IDS rule fully mitigate CVE-2023-0266?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for Linux Kernel run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*