CVE-2026-43186

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).

CVSS v3.1 Score

9.8

CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS — Exploit Prediction

0.0018

Probability of exploitation

0.40%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-787 Out-of-bounds Write

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.15 — 5.15.202
linux	linux_kernel	5.16 — 6.1.165
linux	linux_kernel	6.2 — 6.6.128
linux	linux_kernel	6.7 — 6.12.75
linux	linux_kernel	6.13 — 6.18.16
linux	linux_kernel	6.19 — 6.19.6

References

Advisories & Patches

https://git.kernel.org/stable/c/0591d6509c2ff13f09ea2998434aba0c0472e978 https://git.kernel.org/stable/c/632d233cf2e64a46865ae2c064ae3c9df7c8864f https://git.kernel.org/stable/c/6db8b56eed62baacaf37486e83378a72635c04cc https://git.kernel.org/stable/c/e90346a2f1e8917d5760a44a1f61c44e3b36d96b https://git.kernel.org/stable/c/ea3632aefc04205436868541638e26f4a74d5637 https://git.kernel.org/stable/c/f4d9d4b8fd839719d564651671e24c62c545c23b https://git.kernel.org/stable/c/fb3c662fafebc5b9d74417ed1de8759f6bb72143

Frequently Asked Questions

What is CVE-2026-43186? +

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). It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-43186? +

CVE-2026-43186 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0018, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-43186? +

CVE-2026-43186 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-43186? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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