CriticalCVE-2026-98323

    Linux Kernel: security vulnerability (CVE-2026-98323)

    Published Last modified Sources: SingCERT, Ubuntu, Debian LTS, Debian, HKCERT, SUSE, CVE.org, Msrc Update Guide, BSI

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    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: RDMA/siw: Bound fragmented header copies by the remaining length siw_get_hdr() can receive an extended DDP/RDMAP header across more than one TCP callback. The first callback may receive most of the header, while the next one still limits the copy to hdrlen - MIN_DDP_HDR instead of the number of missing bytes.

    The available sources name no fixed version. Check the vendor guidance in the references below.

    Conflicting version data — version display is hidden until the data is resolved.

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: Vendor (CNA), CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: SingCERT, Ubuntu, Debian LTS, Debian, HKCERT, SUSE, CVE.org, Msrc Update Guide, BSI

    0.5 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 44.0

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    94.28 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.5 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    44.0
    High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    In the Linux kernel, the following vulnerability has been resolved: RDMA/siw: Bound fragmented header copies by the remaining length siw_get_hdr() can receive an extended DDP/RDMAP header across more than one TCP callback. The first callback may receive most of the header, while the next one still limits the copy to hdrlen - MIN_DDP_HDR instead of the number of missing bytes. This makes the destination move past the end of the header and overwrite the receive state, including fpdu_part_rcvd. A later callback can then use a negative fpdu_part_rcvd value as a copy offset, which creates an OOB write. Use the number of header bytes already received when calculating the next copy length.

    Source: CSA/SingCERT, Ubuntu Security Notices, Debian LTS Advisories, Debian Security Advisories, HKCERT (CC BY 3.0 HK) · HKCERT rating: medium, suse_csaf, NVD (NIST), cvelistv5, Microsoft Security Update Guide, BSI WID Portal, BSI CSAF

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    LinuxLinux
    • 6.0.3 – < 6.1
    • 6.19 – < 7.2.8
    • 6.2 – < 6.6.158
    • 5.15.75 – < 5.15.222
    • —
    • 5.4.220 – < 5.5
    • 6.1 – < 6.1.189
    • 5.19.17 – < 5.20
    • 6.7 – < 6.12.112
    • 5.10.150 – < 5.10.271
    • 6.13 – < 6.18.54
    • 6.1
    • 7.2.8
    • 6.6.158
    • 5.15.222
    • 7.3
    • 5.5
    • 6.1.189
    • 5.20
    • 6.12.112
    • 5.10.271
    • 6.18.54

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxtrixie
    Linuxubuntulinuxjammy
    Linuxubuntulinuxresolute
    Linuxdebianlinux-6.12bookworm
    Linuxubuntulinux-awsjammy
    Linuxubuntulinux-awsresolute
    Linuxubuntulinux-aws-5.15focal
    Linuxubuntulinux-aws-fipsjammy
    Linuxubuntulinux-azurejammy
    Linuxubuntulinux-azure-5.15focal
    Linuxubuntulinux-azure-fde-5.15focal
    Linuxubuntulinux-azure-fipsjammy
    Linuxubuntulinux-fipsjammy
    Linuxubuntulinux-gcpjammy
    Linuxubuntulinux-gcpresolute
    Linuxubuntulinux-gcp-5.15focal
    Linuxubuntulinux-gcp-fipsjammy
    Linuxubuntulinux-gkejammy
    Linuxubuntulinux-gkeopjammy
    Linuxubuntulinux-hwe-5.15focal
    Linuxubuntulinux-hwe-7.0noble
    Linuxubuntulinux-ibmjammy
    Linuxubuntulinux-ibmresolute

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedLinux

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/98xxx/CVE-2026-98323.json">CVE-2026-98323</a>

      Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    2. Record modifiedLinux

      CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

      Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

    3. ReceivedLinux

      Description added or changed

      Show 10 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Descriptionadded
      —
      In the Linux kernel, the following vulnerability has been resolved: RDMA/siw: Bound fragmented header copies by the remaining length siw_get_hdr() can receive an extended DDP/RDMAP header across more than one TCP callback. The first callback may receive most of the header, while the next one still limits the copy to hdrlen - MIN_DDP_HDR instead of the number of missing bytes. This makes the destination move past the end of the header and overwrite the receive state, including fpdu_part_rcvd. A later callback can then use a negative fpdu_part_rcvd value as a copy offset, which creates an OOB write. Use the number of header bytes already received when calculating the next copy length.
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/98xxx/CVE-2026-98323.json">CVE-2026-98323</a>
      Referenceadded
      —
      https://git.kernel.org/stable/c/262dcd809723723ed8a4e05437ec7e9c21a8f17e
      Referenceadded
      —
      https://git.kernel.org/stable/c/2c6fbcf4bfac0b2b186acc8d91154c0fa24468a7
      Referenceadded
      —
      https://git.kernel.org/stable/c/8628f8ebf41669302513fb3f0bf0eba38b226742
      Referenceadded
      —
      https://git.kernel.org/stable/c/9ff797e516dbc1ecb73701ec4c24055712d44411
      Referenceadded
      —
      https://git.kernel.org/stable/c/af9f5b474a260ad23ffb9793d716a5e3bbce3b48
      Referenceadded
      —
      https://git.kernel.org/stable/c/b72dcfb9bf1f0f0147cda03dc59e4002a315067f
      Referenceadded
      —
      https://git.kernel.org/stable/c/e6bdfdf3bcb02d0d626a45e8c98b7e63d2fddf9d
      Referenceadded
      —
      https://git.kernel.org/stable/c/eb4d7a946970469b3ab0c762432bf161d5b0836c

      Source identifier: 416baaa9-dc9f-4396-8d5f-8c081fb06d67

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