Linux kernel 'DirtyClone' LPE — SKBFL_SHARED_FRAG drop in __pskb_copy_fclone() + IPsec in-place decrypt; JFrog working exploit on Debian/Ubuntu/Fedora (CVSS 8.8)

DirtyClone Linux kernel LPE (CVE-2026-43503) now has a confirmed working exploit on default Debian/Fedora

UPDATE · originally covered CVE-2026-43503 — Linux kernel "DirtyClone": page-cache corruption via XFRM/IPsec skb cloning (working PoC) (2026-06-27)

JFrog Security Research published a working-exploit write-up for CVE-2026-43503 (DirtyClone, CVSS 8.8), confirmed against Debian, Ubuntu, and Fedora (JFrog Security Research, 2026-06-25 · The Hacker News, 2026-06-29).

__pskb_copy_fclone() drops the SKBFL_SHARED_FRAG flag that marks memory as file-backed during packet cloning; an attacker with CAP_NET_ADMIN (reachable on Debian/Fedora via unprivileged user namespaces by default) wires a privileged binary's pages into a cloned packet, then routes it through an attacker-controlled IPsec tunnel so in-place decryption overwrites in-kernel login checks — granting root with no file-system trace. Mainline is fixed (commit since 2026-05-21); distribution backports are rolling. Until backports land: set kernel.unprivileged_userns_clone=0 on Debian/Ubuntu and blacklist the esp4/esp6 modules to remove the IPsec in-place-decryption primitive. Hunt namespace-creation events granting CAP_NET_ADMIN and su/sudo spawned from non-privileged parents without a TTY.

CVE-2026-43503 (DirtyClone) and CVE-2026-46331 (pedit COW) — Linux kernel LPE with public weaponised PoCs

Two page-cache-corruption local-privilege-escalation flaws drew working exploits within the window. JFrog published a full DirtyClone walkthrough (XFRM/IPsec skb cloning) on 06-25; a companion tc act_pedit out-of-bounds write (pedit COW) gained a weaponised PoC within a day of assignment. Both are post-auth root escalation on patched-but-unrebooted hosts — prioritise kernel updates on multi-tenant and internet-exposed Linux where an initial foothold is plausible.

CVE-2026-43503 — Linux kernel "DirtyClone": page-cache corruption via XFRM/IPsec skb cloning (working PoC)

JFrog Security Research published a full working-exploit walkthrough on 2026-06-25 for DirtyClone, the latest residual variant of the DirtyFrag family (JFrog Security Research, 2026-06-25). The flaw lives in __pskb_copy_fclone(), which fails to preserve the SKBFL_SHARED_FRAG safety flag when cloning a socket buffer; the cloned buffer, still referencing shared file-backed page-cache memory, is then passed through the XFRM/IPsec in-place decryption path, letting attacker-controlled bytes land in the cached image of a setuid binary such as /usr/bin/su (Red Hat, 2026-06-23). Earlier DirtyFrag fixes (CVE-2026-43284, CVE-2026-43500, CVE-2026-46300) do not close this code path; the fix is mainline commit 48f6a5356a33 (Linux v7.1-rc5, merged 2026-05-21), and most distributions had not yet shipped patched kernels at disclosure. The attack leaves no kernel-log or audit-trail artefacts.