CyberSecBulletin
CVE-2026-43186NVD status: Modified

Linux: Out-of-bounds Write

Published Updated By the CyberSecBulletin desk

CVE-2026-43186 is a critical-severity out-of-bounds write vulnerability in Linux, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions f4d9d4b8fd839719d564651671e24c62c545c23b, fb3c662fafebc5b9d74417ed1de8759f6bb72143, 632d233cf2e64a46865ae2c064ae3c9df7c8864f as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.64% chance of exploitation within 30 days, higher than 51% of scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Linux to f4d9d4b8fd839719d564651671e24c62c545c23b or fb3c662fafebc5b9d74417ed1de8759f6bb72143 or 632d233cf2e64a46865ae2c064ae3c9df7c8864f or 0591d6509c2ff13f09ea2998434aba0c0472e978, whichever matches your release line, or a later version.
  2. Update Linux Kernel to 5.15.202 or 6.1.165 or 6.6.128 or 6.12.75, whichever matches your release line, or a later version.
  3. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
LinuxLinux9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 up to, but not including, f4d9d4b8fd839719d564651671e24c62c545c23b; 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 up to, but not including, fb3c662fafebc5b9d74417ed1de8759f6bb72143; 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 up to, but not including, 632d233cf2e64a46865ae2c064ae3c9df7c8864f; 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 up to, but not including, 0591d6509c2ff13f09ea2998434aba0c0472e978; 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 up to, but not including, e90346a2f1e8917d5760a44a1f61c44e3b36d96b; 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 up to, but not including, ea3632aefc04205436868541638e26f4a74d5637; 9ee11f0fff205b4b3df9750bff5e94f97c71b6a0 up to, but not including, 6db8b56eed62baacaf37486e83378a72635c04cc; 5.15f4d9d4b8fd839719d564651671e24c62c545c23b, fb3c662fafebc5b9d74417ed1de8759f6bb72143, 632d233cf2e64a46865ae2c064ae3c9df7c8864f, 0591d6509c2ff13f09ea2998434aba0c0472e978, e90346a2f1e8917d5760a44a1f61c44e3b36d96b, ea3632aefc04205436868541638e26f4a74d5637
LinuxLinux Kernel5.15 up to, but not including, 5.15.202; 5.16 up to, but not including, 6.1.165; 6.2 up to, but not including, 6.6.128; 6.7 up to, but not including, 6.12.75; 6.13 up to, but not including, 6.18.16; 6.19 up to, but not including, 6.19.65.15.202, 6.1.165, 6.6.128, 6.12.75, 6.18.16, 6.19.6

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.

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).

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer.

How developers prevent this class of flaw

  • Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer. Be wary that a language's interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. Examples include the Safe C String Library (SafeStr) by Messier and Viega, and the Strsafe.h library from Microsoft. These libraries provide safer versions of overflow-prone string-handling functions.
  • Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking. D3-SFCV (Stack Frame Canary Validation) from D3FEND discusses canary-based detection in detail.

More Out-of-bounds Write vulnerabilities (CWE-787)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Out-of-bounds Write vulnerabilities

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