Linux Kernel Missing Initialization of a Variable

What to do

1. Update Linux to 3599e6b3cc1ada96883d496a50a210d3afbb6987 or 2f2b16022a2e10ca7bccfb98db5ed2ec0f72641c or 9d3e5fd19fe1063bf607219e8562fbd567b8e8d5 or 78bf6b6bb19541d19fbda6242e7cfe2c682763c0, whichever matches your release line, or a later version.
2. Update SIMATIC S7-1500 CPU 1518-4 PN/DP MFP to V3.1.7 or a later version.
3. Update SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP to V3.1.7 or a later version.
4. CISA's required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

Affected products and versions

Version data comes from the organisation that assigned the CVE; 16 further products are omitted here. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector

LocalThe attacker needs local access or must trick a user into running something.

Attack complexity

LowNo special conditions are needed; the attack works reliably.

Privileges required

LowA basic user account is enough.

User interaction

NoneNo action by a victim is required.

Scope

UnchangedImpact stays within the vulnerable component.

Confidentiality

HighAll data handled by the component can be read.

Integrity

HighData or code can be modified at will.

Availability

HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.

Official description

In the Linux kernel, the following vulnerability has been resolved: net: skbuff: preserve shared-frag marker during coalescing skb_try_coalesce() can attach paged frags from @from to @to. If @from has SKBFL_SHARED_FRAG set, the resulting @to skb can contain the same externally-owned or page-cache-backed frags, but the shared-frag marker is currently lost. That breaks the invariant relied on by later in-place writers. In particular, ESP input checks skb_has_shared_frag() before deciding whether an uncloned nonlinear skb can skip skb_cow_data(). If TCP receive coalescing has moved shared frags into an unmarked skb, ESP can see skb_has_shared_frag() as false and decrypt in place over page-cache backed frags. Propagate SKBFL_SHARED_FRAG when skb_try_coalesce() transfers paged frags. The tailroom copy path does not need the marker because it copies bytes into @to's linear data rather than transferring frag descriptors.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Out-of-bounds Write

Timeline

1. May 14, 2026CISA published its SSVC assessment (exploitation: active, automatable: no, technical impact: total).
2. May 23, 2026CVE record published.
3. October 28, 2026Added to CISA's Known Exploited Vulnerabilities catalogue.
4. October 29, 2026Record last changed materially (score, affected products, status or references).
5. October 31, 2026Deadline for US federal agencies to remediate, set by CISA.

References

Recent Out-of-bounds Write vulnerabilities

• 9.8 Critical severity

  Linux: Out-of-bounds Write

  CVE-2026-43501May 21, 2026Linux
• 7.8 High severity

  Linux: Out-of-bounds Write

  CVE-2026-43498May 21, 2026Linux
• 8.4 High severity

  FreeBSD: Out-of-bounds Write

  CVE-2026-45253May 21, 2026FreeBSD
• 7.5 High severity

  Netatalk: Out-of-bounds Write

  CVE-2026-44062May 21, 2026Netatalk
• 7.5 High severity

  Netatalk: Out-of-bounds Write

  CVE-2026-44049May 21, 2026Netatalk
• 7.5 High severity

  TensorRT: Out-of-bounds Write

  CVE-2026-24188May 20, 2026NVIDIA

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