Vulnerability: Linux kernel IOMMU (AMD) stack buffer overflow from kernel cmdline

CVE: CVE-2025-38676
Severity: Pending at NVD/CNA (VulDB lists as Critical)
Status: Resolved upstream; distributions are rolling out fixes
Affected: Linux kernel up to 6.17-rc2 (IOMMU/AMD path) NVDVulDB

Summary

The AMD IOMMU driver in the Linux kernel had a stack buffer overflow when parsing certain kernel command-line arguments. Under maximum-length input, the code could write one byte past the end of an internal buffer (the acpiid string). Upstream has merged a fix; distros will ship patched kernels. NVDSUSE

 Technical Details (concise)

• Component: iommu/amd

• Bug class: Stack buffer overflow during cmdline parsing (off-by-one) → potential memory corruption early in boot. NVDSUSE

• Scope: Reported against kernels ≤ 6.17-rc2; tagged CVE-2025-38676; fix is upstream. VulDBNVD

• Patch signal: Public patch discussion/series referenced by kernel lists. Spinics

Note: The kernel cmdline is “considered trusted in most environments,” which lowers typical remote exploitability but still demands patching—especially for PXE/automated provisioning and multi-tenant/cloud images. NVD

 Threat Model & Likely Attack Paths

• Preconditions: Attacker can influence kernel boot parameters (e.g., insecure boot chain, compromised PXE/provisioning, physical console/bootloader access).

• Realistic risk: Memory corruption at boot; potential for crash/DoS. Code-exec likelihood is unclear and environment-dependent; treat as defense-in-depth urgent. NVDSUSE

 Mitigation & Patching

1) Patch priority (recommended order):

1. Update to a distro kernel containing the upstream fix (watch SUSE/Red Hat/Ubuntu advisories and apply as released). SUSE

2. For custom kernels: pull the upstream change set corresponding to “iommu/amd: Avoid stack buffer overflow from kernel cmdline,” rebuild, and redeploy. Spinics

2) Boot-chain hardening (defense in depth):

• Lock down bootloader edits (GRUB password, UEFI firmware passwords, disable interactive editing).

• Enforce Secure Boot, restrict unsigned kernels, and control PXE/provisioning pipelines.

• Restrict kexec and enable kernel lockdown on production nodes.

3) Interim ops guidance (while awaiting vendor builds):

• Ensure only approved cmdline parameters are used in images; avoid experimental/over-long AMD IOMMU parameter strings.

• Track distro security feeds for the CVE and schedule emergency maintenance windows to roll kernels quickly. SUSE

 Detection & Hunting

• Signals: Early-boot panics/oops involving iommu/amd; abnormal behavior immediately after boot.

• Where to look:

  • Serial console logs / cloud init logs for boot failures.

  • dmesg (post-boot) for IOMMU warnings or stack traces referencing IOMMU init.

• Preventive controls: Protect/monitor image pipelines; verify cmdline in golden images (/proc/cmdline) matches a hardened baseline.

 Risk Rating (CyberDudeBivash view)

• Exploitability: Low–Medium (requires cmdline influence)

• Impact: Medium–High (kernel-context corruption → potential DoS; worst-case memory safety risk)

• Overall action: Patch ASAP across server, cloud, and VDI fleets.

 Timeline (IST)

• Aug 26, 2025: CVE appears on NVD (“New CVE received from kernel.org”), fix described. NVD

• Aug 26–27, 2025: Vendor trackers (SUSE, VulDB, PT Security) reflect the issue and note upstream resolution. SUSEVulDBDbugs

 References

• NVD: CVE-2025-38676 — description & upstream-resolved note. NVD

• SUSE CVE tracker: Mirrors NVD text and fix status. SUSE

• VulDB: Lists affected as Linux Kernel up to 6.17-rc2, flags Critical. VulDB

• Kernel mailing list (patch thread): “[PATCH RESEND] iommu/amd: Avoid stack buffer overflow from kernel cmdline.” Spinics

 CyberDudeBivash Recommendation

Treat this as a fast patch & harden event. Even if remote exploitation is unlikely, kernel memory safety bugs are a no-debate update—especially in cloud images and automated boot chains. Roll patched kernels, lock the boot path, and verify every image’s cmdline.

Author: CyberDudeBivash • Powered by: CyberDudeBivash
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