Security readout for executives and security teams
Plain-English summary
CVE-2026-23391 is a high-severity Linux kernel netfilter issue. A local user could potentially trigger serious confidentiality, integrity, and availability impact if the system uses affected kernel code paths. The public record shows the issue is resolved in Linux stable commits, but does not show active exploitation.
Executive priority
Treat as a high-priority kernel maintenance item, especially for shared Linux infrastructure and security appliances. It is not currently KEV-listed, so urgency is driven by exposure and patch availability rather than confirmed active attacks.
Technical view
The bug is in netfilter xt_CT template handling. Packets waiting in nfqueue could still refer to template-related objects, such as helpers or timeout policies, after those objects were removed. The kernel fix flushes pending queued packets when a template rule is removed.
Likely exposure
Exposure is most relevant to Linux systems running affected kernel versions with netfilter, xt_CT templates, and nfqueue-related behavior in use. The CVSS vector is local, low-complexity, low-privilege, no user interaction.
Exploitation context
The source bundle marks KEV as false and provides no cited evidence of active exploitation. Public evidence supports local exploitation potential only, not remote unauthenticated exploitation or known weaponization.
Researcher notes
The affected-version data in the bundle is sparse and includes stable commit references rather than complete distribution mappings. Validate against downstream vendor advisories because Linux distributions may backport fixes without changing upstream version numbers.
Mitigation direction
- Check distro or vendor advisories for kernel packages containing the stable fixes.
- Prioritize kernel updates on multi-user, container-host, firewall, and appliance Linux systems.
- Review Siemens advisories if using Siemens products that embed Linux.
- Apply vendor-supported mitigations only if patching is delayed.
Validation and detection
- Inventory Linux kernel versions across servers, appliances, and embedded products.
- Check whether running kernels include the referenced stable commits or vendor backports.
- Identify systems using netfilter, nfqueue, or xt_CT template functionality.
- Confirm patched kernels after reboot, not only package installation.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CVE-2026-23391 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
- 7.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H1.85.9LinuxVulnerability scoring details
Base CVSS 3.1 score
7.8HighVector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/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.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://git.kernel.org/stable/c/55445134d42b84cb0a272e42c98d233ca65eca83CVE reference, Linux
- https://git.kernel.org/stable/c/cc57506dd66555899560b9c0f24e813f034e12ecCVE reference, Linux
- https://git.kernel.org/stable/c/d2d0bae0c9a2a17b6990a2966f5cdce0813d6256CVE reference, Linux
- https://git.kernel.org/stable/c/63b8097cea1923fe82cd598068d0796da8c015ecCVE reference, Linux
- https://git.kernel.org/stable/c/19a230dec6bb8928e3f96387f9085cf2c79bcef9CVE reference, Linux
- https://git.kernel.org/stable/c/cb549925875fa06dd155e49db4ac2c5044c30f9cCVE reference, Linux
- https://git.kernel.org/stable/c/777d02efe3d630cca4c1b63962cec17c57711325CVE reference, Linux
- https://git.kernel.org/stable/c/f62a218a946b19bb59abdd5361da85fa4606b96bCVE reference, Linux
- https://cert-portal.siemens.com/productcert/html/ssa-082556.htmlCVE reference, siemens-SADP
- https://cert-portal.siemens.com/productcert/html/ssa-019113.htmlCVE reference, siemens-SADP
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.