CVE-2026-43500 Linux CVE debrief

Who should care

Linux kernel and distro security teams, kernel maintainers, and administrators running affected kernels should care most. The CVSS vector is local (AV:L) with low privileges required (PR:L), so this is primarily a host-side risk on systems where local users or local services can reach the affected rxrpc paths.

Technical summary

The supplied description says rxrpc_input_call_event() and rxrpc_verify_response() only copied skb buffers to a linear buffer when skb_cloned() was true. That missed packets with shared paged fragments, including cases where skb_has_frag_list() or skb_has_shared_frag() is true. The fix extends the unshare check to those fragment-sharing conditions before security operations and decryption, preserving the zero-copy path for kernel-private fragments while avoiding unsafe handling of externally-owned pages. NVD maps the weakness to CWE-787.

Defensive priority

High. The issue is local rather than remote, but it affects core kernel packet processing and carries a high CVSS score. Prioritize patching affected kernels and confirm that vendor backports are present on deployed systems.

Recommended defensive actions

• Upgrade to a kernel version that includes the fix; NVD lists affected ranges as Linux kernel versions before 6.18.29 and 6.19 through before 7.0.6, plus the specific release-candidate builds called out in the record.
• Verify that your distribution's kernel package includes the backported rxrpc fix, since vendor kernels may not align exactly with upstream version numbers.
• If rxrpc is enabled or in use on your systems, place these hosts high in your patch queue, especially multi-user machines where local access is feasible.
• Monitor vendor advisories and kernel changelogs for the linked stable patch references to confirm remediation has been applied.
• Use standard hardening and least-privilege controls to reduce the likelihood that an untrusted local user can reach the affected code paths before patching.

Evidence notes

This debrief is based only on the supplied NVD record, its published/modified dates (published 2026-05-11, modified 2026-05-17), and the linked kernel references. The record describes an rxrpc packet-handling unshare check that failed to account for shared paged fragments, and it classifies the issue as CWE-787 with a local CVSS 7.8 score. No exploit code, weaponized reproduction, or unsupported impact claims are included.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.