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CVE-2026-81003 high CVSS 8.1

Vulnerability in Linux kernel (CVE-2026-81003)

Summary

Vulnerability in Linux kernel (CVE-2026-81003). Data can be tampered with by attackers.

Original description

The description as published by the source.

In the Linux kernel, the following vulnerability has been resolved:

net/iucv: filter frames in afiucv_hs_rcv() by ingress device

afiucv_hs_rcv() selects a socket from iucv_sk_list by matching four 8-byte
name fields in the transport header alone. No check is made against the
net_device the frame arrived on.

This can cause a frame arriving on any netdev to be delivered to an AF_IUCV
socket. Three problems follow.

First, a frame arriving over HiperSockets can be delivered to a socket
bound to the classic z/VM IUCV transport, which has iucv->hs_dev == NULL.
iucv_sock_bind() takes the classic path whenever the requested userid
matches iucv_userid, even on a guest that also has a HiperSockets device
carrying the same identifier. The child socket created by
afiucv_hs_callback_syn() for such a match inherits hs_dev = NULL and
transport = AF_IUCV_TRANS_HIPER, so the first send() on it returns -ENODEV.
The socket delivered to accept() is unusable.

Second, a frame arriving on one netdev can be delivered to a socket bound
to a different IQD device. Which can lead to

  • Accept-queue exhaustion (DoS)
  • Attacker-controlled peer identity in the child socket
  • Data injection into existing sockets
  • Fabric noise on the IQD fabric, where bogus replies are sent
  • killing established connections

Third, all AF_IUCV sockets live in init_net, as iucv_sock_alloc() calls
sk_alloc(&init_net, ...). But even frames arriving on netdev devices in a
namespace can be delivered to an IUCV socket. So a p…

Source: NIST National Vulnerability Database NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-81003 has been found in Linux kernel.
Data can be tampered with by attackers. CVSS score: 8.1/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-81003" on the vendor's site.

CVE-2026-81003 (Linux kernel) — CVSS v3 8.1
Attack vector: adjacent-network / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) exists in Linux kernel.

📍 Affected scope

Check the vendor advisory for the affected versions of Linux kernel.

🔥 Severity

Severity: High (CVSS 8.1/10). Data can be tampered with by attackers.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。

  2. 2
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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