Security readout for executives and security teams
Plain-English summary
A malformed TCP option can make Linux netfilter read past the intended buffer while processing TCP maximum-segment-size information. The supplied CVSS score is 8.2 because unauthenticated network traffic may trigger limited information exposure or serious service disruption. The evidence does not establish code execution.
Executive priority
Treat this as a high-priority kernel update for exposed network infrastructure. Accelerate assessment and patching on internet-facing packet-processing systems; schedule other Linux hosts according to reachability and vendor guidance. Current evidence supports urgency but not an emergency claim of active exploitation.
Technical view
The xt_tcpmss TCP option parser reads op[i+1] without first confirming that a second option byte remains. A final option byte other than EOL or NOP can therefore cause an out-of-bounds read beyond the option boundary, potentially reaching the stack buffer boundary or subsequent packet payload.
Likely exposure
Prioritize Linux routers, firewalls, gateways, and hosts where netfilter's xt_tcpmss processing handles untrusted TCP traffic. The source lists Linux versions from 2.6.12 through affected stable-series boundaries, but distribution kernels may contain backports; package versions alone cannot conclusively determine exposure.
Exploitation context
The CVSS vector describes remote, low-complexity, unauthenticated exploitation requiring no user interaction. However, the supplied record is not in KEV and provides no evidence of active exploitation or a public working exploit. Confirm reachable packet-processing conditions before treating every Linux host as equally exposed.
Researcher notes
No CWE is assigned in the supplied record. The defect is a one-byte-boundary validation failure in TCP option parsing. Stable-kernel commit references document branch-specific corrections. Public evidence supplied here does not establish practical crash reliability, information recovery, code execution, or exploitation in the wild.
Mitigation direction
- Apply a vendor-supported kernel containing the relevant stable fix for your kernel branch.
- Prioritize internet-facing gateways, firewalls, and systems processing untrusted TCP traffic.
- Reboot into the updated kernel when required by the distribution's guidance.
- If immediate updating is impossible, consult vendor guidance for supported temporary mitigations.
Validation and detection
- Inventory running kernel versions across Linux systems, emphasizing network-edge infrastructure.
- Check distribution advisories for backported fixes rather than relying only on upstream version numbers.
- Confirm the running kernel includes the applicable upstream stable commit or vendor equivalent.
- Determine whether xt_tcpmss processing is enabled and reachable by untrusted TCP traffic.
- After remediation, verify systems are running the updated kernel, not merely storing it.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CVE-2026-43190 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.2 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H3.94.2LinuxVulnerability scoring details
Base CVSS 3.1 score
8.2HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/f895191dc32c53eaf443b6443fe40945b2f92287CVE reference, Linux
- https://git.kernel.org/stable/c/cd5beda7e0e32865e214f28034bb92c1cecff885CVE reference, Linux
- https://git.kernel.org/stable/c/eaedc0bc18be46fe7f58170e967959a932c4f824CVE reference, Linux
- https://git.kernel.org/stable/c/07a9b32eaae792ff7d0fcac14d8920c937c0a9c3CVE reference, Linux
- https://git.kernel.org/stable/c/8b300f726640c48c3edfe9c453334dd801f4b74eCVE reference, Linux
- https://git.kernel.org/stable/c/5e13d0a37666955b6cfddc0f73cb40ed645b8a05CVE reference, Linux
- https://git.kernel.org/stable/c/f6c412dcfd76b0516d51aa847d8f4c7b70381b09CVE reference, Linux
- https://git.kernel.org/stable/c/735ee8582da3d239eb0c7a53adca61b79fb228b3CVE reference, Linux
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.