⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Not verified

How to Fix CVE-2026-31690: firmware: thead: Fix buffer overflow and use standard endian macros in Linux

By Sai Kiran Pandrala

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

Last verified: 2026-05-25

CVE-2026-31690 is a firmware: thead: fix buffer overflow and use standard endian macros in Linux Linux. Fix it by upgrading to 6.18.23, 6.19.13, 7.0.

⚡ At a glance
SeverityNot verified - see official advisory
Actively exploited?Not currently in the CISA KEV catalog
AffectedLinux e4b3cbd840e565484d0ad8d260d27c057466ed17 up to (excluding) fbdb43f6bb2a15ed382d6eb0ef82c8b07b0d47bb; Linux e4b3cbd840e565484d0ad8d260d27c057466ed17 up to (excluding) bd15a5deb5a7251dc1a0cf9186f0253f7eacdb97; Linux e4b3cbd840e565484d0ad8d260d27c057466ed17 up to (excluding) 88c4bd90725557796c15878b7cb70066e9e6b5ab; Linux 6.15
Fixed in6.18.23, 6.19.13, 7.0
Type (CWE)Not verified

What is CVE-2026-31690?

CVE-2026-31690 is a firmware: thead: fix buffer overflow and use standard endian macros flaw in Linux Linux. The vendor has not published a verified CVSS metric at the time of writing. It is not currently listed in the CISA Known Exploited Vulnerabilities catalog.

From the source record: In the Linux kernel, the following vulnerability has been resolved:

firmware: thead: Fix buffer overflow and use standard endian macros

Addresses two issues in the TH1520 AON firmware protocol driver:

  1. Fix a potential buffer overflow where the code used unsafe pointer

arithmetic to access the 'mode' field through the 'resource' pointer

with an offset. This was flagged by Smatch static checker as:

"buffer overflow 'data' 2 <= 3"

  1. Replace custom RPC_SET_BE* and RPC_GET_BE* macros with standard

kernel endianness conversion macros (cpu_to_be16, etc.) for better

portability and maintainability.

The functionality was re-tested with the GPU power-up sequence,

confirming the GPU powers up correctly and the driver probes

successfully.

[ 12.702370] powervr ffef400000.gpu: [drm] loaded firmware

powervr/rogue_36.52.104.182_v1.fw

[ 12.711043] powervr ffef400000.

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 Linux matches a version listed in the Affected row above.


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

How to fix CVE-2026-31690

Apply the vendor patch. Target the build named in the Fixed in row above (6.18.23, 6.19.13, 7.0). The runnable command set below covers the most common deployment patterns for Linux.

Ubuntu / Debian


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

RHEL / CentOS / Rocky


sudo dnf upgrade linux -y
rpm -q linux

After applying the patch

  1. Restart the service or device so the patched binary loads.
  2. Confirm the running version matches the Fixed in row using the verification command below.
  3. 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.

How to verify the fix worked

Confirm the patched build is the one actually running.


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

Expected: a version at or above 6.18.23, 6.19.13, 7.0.

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-2026-31690 being exploited in the wild?

As of 2026-05-25, CVE-2026-31690 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-2026-31690?

A verified CVSS score is not listed in the public record for CVE-2026-31690. Check the vendor advisory and the NVD page for an updated metric.

What version fixes this?

Upgrade to 6.18.23, 6.19.13, 7.0.

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.

References

*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.*