# CVE-2026-43186: ipv6: ioam: fix heap buffer overflow in __ioam6_fill_trace_data() > A crafted IPv6 packet triggers a heap buffer overflow in the Linux kernel's IOAM module, causing memory corruption and a kernel panic. - **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 6 May 2026 - **Updated:** 19 Oct 2026 - **Also known as:** ALSA-2026:51295, BELL-CVE-2026-43186, DEBIAN-CVE-2026-43186, GHSA-8x8h-4g2v-qpf2, RHSA-2026:51295, RLSA-2026:51295, ROOT-OS-UBUNTU-2204-CVE-2026-43186, ROOT-OS-UBUNTU-2404-CVE-2026-43186, UBUNTU-CVE-2026-43186 ## What is CVE-2026-43186? CVE-2026-43186 is a critical memory corruption vulnerability in Linux kernel, published on 6 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description In the Linux kernel, the following vulnerability has been resolved: ipv6: ioam: fix heap buffer overflow in __ioam6_fill_trace_data() On the receive path, __ioam6_fill_trace_data() uses trace->nodelen to decide how much data to write for each node. It trusts this field as-is from the incoming packet, with no consistency check against trace->type (the 24-bit field that tells which data items are present). A crafted packet can set nodelen=0 while setting type bits 0-21, causing the function to write ~100 bytes past the allocated region (into skb_shared_info), which corrupts adjacent heap memory and leads to a kernel panic. Add a shared helper ioam6_trace_compute_nodelen() in ioam6.c to derive the expected nodelen from the type field, and use it: - in ioam6_iptunnel.c (send path, existing validation) to replace the open-coded computation; - in exthdrs.c (receive path, ipv6_hop_ioam) to drop packets whose nodelen is inconsistent with the type field, before any data is written. Per RFC 9197, bits 12-21 are each short (4-octet) fields, so they are included in IOAM6_MASK_SHORT_FIELDS (changed from 0xff100000 to 0xff1ffc00). Weakness: CWE-787 (Out-of-bounds Write), CWE-122 (Heap-based Buffer Overflow) ## Which versions are affected by CVE-2026-43186? It affects 1 product. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `kernel` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-core` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-debug` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-debug-core` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-debug-devel` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-debug-devel-matched` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-debug-modules` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-debug-modules-core` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-debug-modules-extra` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-devel` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-devel-matched` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-modules` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-modules-core` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-64k-modules-extra` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-abi-stablelists` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-core` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-cross-headers` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-debug` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-debug-core` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-debug-devel` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-debug-devel-matched` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-debug-modules` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-debug-modules-core` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-debug-modules-extra` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-debug-uki-virt` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-devel` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-devel-matched` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-doc` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-headers` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-modules` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-modules-core` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-modules-extra` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-modules-extra-matched` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-rt` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-rt-64k` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-rt-64k-core` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-rt-64k-debug` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-rt-64k-debug-core` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | | `kernel-rt-64k-debug-devel` | AlmaLinux:10 | All versions | 6.12.0-211.44.1.el10_2 | Products: Linux kernel. ## How do I fix CVE-2026-43186? Apply the vendor's patch. ## Is CVE-2026-43186 being exploited? There is no known exploitation of CVE-2026-43186 in the wild and no public exploit code. ## Other vulnerabilities in Linux kernel - [CVE-2026-53266](https://insights.sbomify.com/CVE-2026-53266/): Linux Kernel Out-of-Bounds Write (high 8.8, exploited in the wild) - [CVE-2013-6282](https://insights.sbomify.com/CVE-2013-6282/): Linux Kernel Improper Input Validation (high 8.8, exploited in the wild) - [CVE-2022-0185](https://insights.sbomify.com/CVE-2022-0185/): Linux Kernel Heap-Based Buffer Overflow (high 8.4, exploited in the wild) - [CVE-2013-2094](https://insights.sbomify.com/CVE-2013-2094/): Linux Kernel Privilege Escalation (high 8.4, exploited in the wild) - [CVE-2026-53362](https://insights.sbomify.com/CVE-2026-53362/): Linux Kernel Unspecified (high 7.8, exploited in the wild) ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-43186 and fix it if it is affected. What it is: CVE-2026-43186 is a critical memory corruption vulnerability in Linux kernel, published on 6 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-43186 in the wild and no public exploit code. Affected product: Linux kernel. No package-level version data is available, so check the vendor advisory linked from the reference page. Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-43186/ (Markdown: https://insights.sbomify.com/CVE-2026-43186/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43186 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43186 - OSV: https://osv.dev/vulnerability/CVE-2026-43186 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-43186/ Summaries are generated and may contain mistakes; the official description above is the record.