MediumCVE-2026-43492

    Linux Kernel: Integer Underflow (CVE-2026-43492)

    Published Last modified Sources: Siemens ProductCERT, Debian LTS, SUSE, Ubuntu, BSI, EUVD, CVE.org, Msrc Update Guide

    What is affected, what to do

    In the Linux kernel, the following vulnerability has been resolved: lib/crypto: mpi: Fix integer underflow in mpi_read_raw_from_sgl() Yiming reports an integer underflow in mpi_read_raw_from_sgl() when subtracting "lzeros" from the unsigned "nbytes". For this to happen, the scatterlist "sgl" needs to occupy more bytes than the "nbytes" parameter and the first "nbytes + 1" bytes of the scatterlist must be zero.

    Update Linux Kernel to version 5.10.259, Linux Kernel to version 5.15.210, Linux Kernel to version 6.1.176.

    Affected
    • Linux Kernel lt 4.4..5.10.259
    • Linux Kernel lt 5.11..5.15.210
    • Linux Kernel lt 5.16..6.1.176
    • Linux Kernel lt 6.2..6.6.140
    • Linux Kernel lt 6.7..6.12.88
    • Linux Kernel lt 6.13..6.18.30
    • Linux Kernel lt 6.19..7.0.7
    Fixed in
    • Linux Kernel 5.10.259
    • Linux Kernel 5.15.210
    • Linux Kernel 6.1.176
    • Linux Kernel 6.6.140
    • Linux Kernel 6.12.88
    • Linux Kernel 6.18.30
    • Linux Kernel 7.0.7
    • Linux Kernel 7.1

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

    Metrics

    5.5

    Priority

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

    Source: NVD, CVSS v3

    5.5

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: Siemens ProductCERT, Debian LTS, SUSE, Ubuntu, BSI, EUVD, CVE.org, Msrc Update Guide

    0.2 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 4.8

    Show all metrics
    Severity
    Medium
    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
    45.20 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
    5.5 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
    5.5
    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
    0.2 %
    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
    4.8
    Low — this CVE sits in the lower 10% of all CVEs scored today.
    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
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    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: lib/crypto: mpi: Fix integer underflow in mpi_read_raw_from_sgl() Yiming reports an integer underflow in mpi_read_raw_from_sgl() when subtracting "lzeros" from the unsigned "nbytes". For this to happen, the scatterlist "sgl" needs to occupy more bytes than the "nbytes" parameter and the first "nbytes + 1" bytes of the scatterlist must be zero. Under these conditions, the while loop iterating over the scatterlist will count more zeroes than "nbytes", subtract the number of zeroes from "nbytes" and cause the underflow. When commit 2d4d1eea540b ("lib/mpi: Add mpi sgl helpers") originally introduced the bug, it couldn't be triggered because all callers of mpi_read_raw_from_sgl() passed a scatterlist whose length was equal to "nbytes". However since commit 63ba4d67594a ("KEYS: asymmetric: Use new crypto interface without scatterlists"), the underflow can now actually be triggered. When invoking a KEYCTL_PKEY_ENCRYPT system call with a larger "out_len" than "in_len" and filling the "in" buffer with zeroes, crypto_akcipher_sync_prep() will create an all-zero scatterlist used for both the "src" and "dst" member of struct akcipher_request and thereby fulfil the conditions to trigger the bug: sys_keyctl() keyctl_pkey_e_d_s() asymmetric_key_eds_op() software_key_eds_op() crypto_akcipher_sync_encrypt() crypto_akcipher_sync_prep() crypto_akcipher_encrypt() rsa_enc() mpi_read_raw_from_sgl() To the user this will be visible as a DoS as the kernel spins forever, causing soft lockup splats as a side effect. Fix it.

    Source: siemens_advisory, Debian LTS Advisories, suse_csaf, Ubuntu Security Notices, BSI WID Portal, BSI CSAF, ENISA EUVD, cvelistv5, NVD (NIST), Microsoft Security Update Guide, CVE.org (MITRE)

    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
    • 6.7 – < 6.12.88
    • 6.2 – < 6.6.140
    • 5.11 – < 5.15.210
    • 6.19 – < 7.0.7
    • —
    • 5.16 – < 6.1.176
    • 6.13 – < 6.18.30
    • 4.4 – < 5.10.259
    • 6.12.88
    • 6.6.140
    • 5.15.210
    • 7.0.7
    • 7.1
    • 6.1.176
    • 6.18.30
    • 5.10.259
    SiemensSIMATIC S7
    • 1500 TM MFP V1.1.1 GNU/Linux subsystem
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianlinuxbookworm
    Linuxdebianlinuxbullseye
    Linuxdebianlinux-6.1bullseye
    Linuxubuntulinux-oracle-7.0noble
    Linuxlinuxlinux_kernel—

    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 modifiedSiemens ADP

      Show 3 original changes
      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/2026/43xxx/CVE-2026-43492.json">CVE-2026-43492</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-457936.html
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-784472.html

      Source identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

    2. Record modifiedLinux

      Show 24 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/1abd50fc3cfa16fc2074a3c8c2729c50fd9d7043
      Referenceadded
      —
      https://git.kernel.org/stable/c/26d3a97ad46c7a9226ec04d4bf35bd4998a97d16
      Referenceadded
      —
      https://git.kernel.org/stable/c/2aa77a18dc7f2670497fe3ee5acbeda0b57659e5
      Referenceadded
      —
      https://git.kernel.org/stable/c/30e513e755bb381afce6fb57cdc8694136193f22
      Referenceadded
      —
      https://git.kernel.org/stable/c/6d63615c796c085b4984e3031b9fa77fffb47360
      Referenceadded
      —
      https://git.kernel.org/stable/c/8637dfb4c1d8a7026ef681f2477c6de8b71c4003
      Referenceadded
      —
      https://git.kernel.org/stable/c/8c2f1288250a90a4b5cabed5d888d7e3aeed4035
      Referenceadded
      —
      https://git.kernel.org/stable/c/a1793a48881ec8d26e9c79b0ee65753f1c6846a4
      Referenceremoved
      https://git.kernel.org/stable/c/1abd50fc3cfa16fc2074a3c8c2729c50fd9d7043
      —
      Referenceremoved
      https://git.kernel.org/stable/c/26d3a97ad46c7a9226ec04d4bf35bd4998a97d16
      —
      Referenceremoved
      https://git.kernel.org/stable/c/2aa77a18dc7f2670497fe3ee5acbeda0b57659e5
      —
      Referenceremoved
      https://git.kernel.org/stable/c/30e513e755bb381afce6fb57cdc8694136193f22
      —
      Referenceremoved
      https://git.kernel.org/stable/c/6d63615c796c085b4984e3031b9fa77fffb47360
      —
      Referenceremoved
      https://git.kernel.org/stable/c/8637dfb4c1d8a7026ef681f2477c6de8b71c4003
      —
      Referenceremoved
      https://git.kernel.org/stable/c/8c2f1288250a90a4b5cabed5d888d7e3aeed4035
      —
      Referenceremoved
      https://git.kernel.org/stable/c/a1793a48881ec8d26e9c79b0ee65753f1c6846a4
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/1abd50fc3cfa16fc2074a3c8c2729c50fd9d7043 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/26d3a97ad46c7a9226ec04d4bf35bd4998a97d16 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/2aa77a18dc7f2670497fe3ee5acbeda0b57659e5 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/30e513e755bb381afce6fb57cdc8694136193f22 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/6d63615c796c085b4984e3031b9fa77fffb47360 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/8637dfb4c1d8a7026ef681f2477c6de8b71c4003 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/8c2f1288250a90a4b5cabed5d888d7e3aeed4035 Types: Patch
      —
      Reference typeremoved
      https://git.kernel.org/stable/c/a1793a48881ec8d26e9c79b0ee65753f1c6846a4 Types: Patch
      —

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

    3. Record modifiedSiemens ADP

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/43xxx/CVE-2026-43492.json">CVE-2026-43492</a>
      Referenceadded
      —
      https://cert-portal.siemens.com/productcert/html/ssa-019113.html

      Source identifier: 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e

    4. Record modifiedLinux

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://git.kernel.org/stable/c/1abd50fc3cfa16fc2074a3c8c2729c50fd9d7043
      Referenceadded
      —
      https://git.kernel.org/stable/c/6d63615c796c085b4984e3031b9fa77fffb47360
      Referenceadded
      —
      https://git.kernel.org/stable/c/a1793a48881ec8d26e9c79b0ee65753f1c6846a4
      Affected versions (publisher)changed
      Linux, Linux
      Linux, Linux

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

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