● High · CVSS 7.8

How to Fix CVE-2026-33999: Integer Underflow (Wrap or Wraparound) in Red Hat Enterprise Linux 10

Last verified: 2026-05-25

CVE-2026-33999 is a integer underflow (wrap or wraparound) in Red Hat Red Hat Enterprise Linux 10. Fix it by upgrading to 0:24.1.5-6.el10_1, 0:24.1.9-4.el10_2, 0:21.1.3-20.el8_10, 0:1.20.11-28.el8_10, 0:1.15.0-9.el8_10, 0:1.15.0-6.el9_7.1.

⚡ At a glance

Severity	CVSS 7.8 - High
Actively exploited?	Not currently in the CISA KEV catalog
Affected	See vendor advisory for affected versions
Fixed in	0:24.1.5-6.el10_1, 0:24.1.9-4.el10_2, 0:21.1.3-20.el8_10, 0:1.20.11-28.el8_10, 0:1.15.0-9.el8_10, 0:1.15.0-6.el9_7.1
Type (CWE)	CWE-191: Integer Underflow (Wrap or Wraparound)

Exploitation status

CISA has not added CVE-2026-33999 to its Known Exploited Vulnerabilities (KEV) catalog, meaning there is no government-confirmed evidence of active exploitation yet. Do not read that as all-clear: the KEV catalog often trails real-world attacks, so prioritise this on its severity rather than waiting for a listing.

Public exploit availability: no public proof-of-concept or Metasploit module is referenced in this record yet. That says nothing about private exploit code, so do not treat the issue as low risk just because none is published.

Authoritative references:

What is CVE-2026-33999?

CVE-2026-33999 is a integer underflow (wrap or wraparound) flaw in Red Hat Red Hat Enterprise Linux 10. It carries a CVSS base score of 7.8 (high). It is not currently listed in the CISA Known Exploited Vulnerabilities catalog.

From the source record: A flaw was found in the X.Org X server. This integer underflow vulnerability, specifically in the XKB compatibility map handling, allows an attacker with local or remote X11 server access to trigger a buffer read overrun. This can lead to memory-safety violations and potentially a denial of service (DoS) or other severe impacts.

Why it matters in practice: The blast radius depends on how the affected service is exposed. An internet-facing instance with no compensating controls is the highest-risk configuration.

Am I affected?

You are affected if your installation of Red Hat Enterprise Linux 10 matches a version listed in the Affected row above.

# Debian/Ubuntu
dpkg -s red | grep Version
# RHEL/Rocky
rpm -q red

How to fix CVE-2026-33999

Apply the vendor patch. Target the build named in the Fixed in row above (0:24.1.5-6.el10_1, 0:24.1.9-4.el10_2, 0:21.1.3-20.el8_10, 0:1.20.11-28.el8_10, 0:1.15.0-9.el8_10, 0:1.15.0-6.el9_7.1). The runnable command set below covers the most common deployment patterns for Red Hat Enterprise Linux 10.

Ubuntu / Debian

sudo apt-get update
sudo apt-get install --only-upgrade red
dpkg -s red | grep Version

RHEL / CentOS / Rocky

sudo dnf upgrade red -y
rpm -q red

After applying the patch

Restart the service or device so the patched binary loads.
Confirm the running version matches the Fixed in row using the verification command below.
Rotate credentials and API keys that the affected service could access if the asset was exposed during the disclosure window.

If you can't patch immediately

Until the patch lands, narrow the attack surface with these runnable controls.

Restrict network exposure

Block public access to the affected service at the perimeter. Allow only trusted source IPs.

# Linux iptables: only allow trusted admin subnet
sudo iptables -A INPUT -p tcp --dport 443 -s 10.10.10.0/24 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 443 -j DROP
sudo iptables-save | sudo tee /etc/iptables/rules.v4

# Windows firewall: only allow trusted admin subnet on management port
New-NetFirewallRule -DisplayName "Restrict-Mgmt-Allow" -Direction Inbound -Action Allow `
  -RemoteAddress 10.10.10.0/24 -Protocol TCP -LocalPort 443
New-NetFirewallRule -DisplayName "Restrict-Mgmt-Deny"  -Direction Inbound -Action Block `
  -Protocol TCP -LocalPort 443

Mitigations are temporary. Apply the vendor patch as soon as a maintenance window opens.

The repair

Confirm the patched build is the one actually running.

# Debian/Ubuntu
dpkg -s red | grep Version
# RHEL/Rocky
rpm -q red

Expected: a version at or above 0:24.1.5-6.el10_1, 0:24.1.9-4.el10_2, 0:21.1.3-20.el8_10, 0:1.20.11-28.el8_10, 0:1.15.0-9.el8_10, 0:1.15.0-6.el9_7.1.

Also worth doing: pull recent log windows for indicators of compromise listed in the vendor advisory, and re-run an authenticated vulnerability scan with up-to-date signatures.

Frequently asked questions

Is CVE-2026-33999 being exploited in the wild?

As of 2026-05-25, CVE-2026-33999 is not listed in the CISA Known Exploited Vulnerabilities catalog. Watch the catalog and patch on a normal cadence; KEV status can change as exploitation evidence emerges.

What is the CVSS score for CVE-2026-33999?

The CVSS base score is 7.8 (High).

What version fixes this?

Upgrade to 0:24.1.5-6.el10_1, 0:24.1.9-4.el10_2, 0:21.1.3-20.el8_10, 0:1.20.11-28.el8_10, 0:1.15.0-9.el8_10, 0:1.15.0-6.el9_7.1.

Will a WAF or IDS rule alone close this?

No. Network filters cut down opportunistic scans but they do not remove the flaw. The vendor patch is the only durable fix.

Other defects in the same area that deserve attention during this patch cycle:

References

Official vendor advisory: https://access.redhat.com/errata/RHSA-2026:10739
NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2026-33999
CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Additional reference: https://access.redhat.com/errata/RHSA-2026:11352
Additional reference: https://access.redhat.com/errata/RHSA-2026:11369
Additional reference: https://access.redhat.com/errata/RHSA-2026:11388
Additional reference: https://access.redhat.com/errata/RHSA-2026:11656

Assembled from the official vendor advisory, the NVD record, and the CISA KEV listing on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.

What you'll see

When this symptom shows up on this unit, three patterns repeat:

1. Recent firmware update changed behavior, the symptom started within a week of an OTA push. Rollback or wait for the hotfix. 2. Environmental trigger. temperature, humidity, line voltage, network changes. Look at what changed in the environment. 3. Cumulative wear, components like batteries, gaskets, fans degrade over time. Replace the consumable rather than chasing a software fix.

Knowing which pattern applies saves time on the wrong fix.

Why it happens

A few things to confirm so the device fix goes cleanly:

Latest firmware downloaded if you're going to update.
Warranty + support contract status checked: opening sealed parts may void it.
Backup of current configuration (where applicable) taken.
Spare parts on hand if you anticipate replacement.
Adequate workspace, lighting, and time, rushing causes regressions.

Verification checks

Before you walk away from the device in front of you fix, run through:

1. Reproduce the original trigger. does the issue reappear? 2. Check the device's status / health screen for any new alerts. 3. Confirm paired devices (app, hub, controller) reconnected. 4. Save / commit any configuration changes per the device's normal workflow. 5. Note the change in your maintenance log with date + firmware version.

When to call How support instead

Escalate if:

The same symptom returns within 24 hours of a clean fix.
You see physical damage (burn marks, swollen battery, cracked PCB).
The device is in warranty and a hardware replacement is the cheaper outcome.
Repair requires specialised tools you don't own (alignment jigs, calibration software).
Following the official path keeps the warranty intact, which matters more than the time spent.