CVE-2026-43190

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_tcpmss: check remaining length before reading optlen Quoting reporter: In net/netfilter/xt_tcpmss.c (lines 53-68), the TCP option parser reads op[i+1] directly without validating the remaining option length. If the last byte of the option field is not EOL/NOP (0/1), the code attempts to index op[i+1]. In the case where i + 1 == optlen, this causes an out-of-bounds read, accessing memory past the optlen boundary (either reading beyond the stack buffer _opt or the following payload).

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CVSS v3.1 Score

8.2

HIGH

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

EPSS — Exploit Prediction

0.0007

Probability of exploitation

0.21%

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-125 Out-of-bounds Read

Affected Products

Vendor	Product	Versions
linux	linux_kernel	2.6.12.1 — 5.10.252
linux	linux_kernel	5.11 — 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
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/07a9b32eaae792ff7d0fcac14d8920c937c0a9c3 https://git.kernel.org/stable/c/5e13d0a37666955b6cfddc0f73cb40ed645b8a05 https://git.kernel.org/stable/c/735ee8582da3d239eb0c7a53adca61b79fb228b3 https://git.kernel.org/stable/c/8b300f726640c48c3edfe9c453334dd801f4b74e https://git.kernel.org/stable/c/cd5beda7e0e32865e214f28034bb92c1cecff885 https://git.kernel.org/stable/c/eaedc0bc18be46fe7f58170e967959a932c4f824 https://git.kernel.org/stable/c/f6c412dcfd76b0516d51aa847d8f4c7b70381b09 https://git.kernel.org/stable/c/f895191dc32c53eaf443b6443fe40945b2f92287

Frequently Asked Questions

What is CVE-2026-43190? +

In the Linux kernel, the following vulnerability has been resolved: netfilter: xt_tcpmss: check remaining length before reading optlen Quoting reporter: In net/netfilter/xt_tcpmss.c (lines 53-68), the TCP option parser reads op[i+1] directly without validating the remaining option length. If the last byte of the option field is not EOL/NOP (0/1), the code attempts to index op[i+1]. In the case where i + 1 == optlen, this causes an out-of-bounds read, accessing memory past the optlen boundary (either reading beyond the stack buffer _opt or the following payload). It has a CVSS v3.1 base score of 8.2 (HIGH).

How severe is CVE-2026-43190? +

CVE-2026-43190 has a CVSS v3.1 score of 8.2 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0007, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-43190? +

CVE-2026-43190 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-2026-43190? +

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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