CC-4779 - Proof-of

CVE‑2026‑43284 and CVE‑2026‑43500 (dubbed as "Dirty Frag"), when chained together, could allow an unprivileged attacker to achieve root privileges on Linux distributions

CVE‑2026‑43284 and CVE‑2026‑43500 (dubbed as "Dirty Frag"), when chained together, could allow an unprivileged attacker to achieve root privileges on Linux distributions

The following platforms are known to be affected:

Linux kernel versions

“Dirty Frag” vulnerabilities have been tested on the following distribution versions (but not limited to)

Note: Systems with the publicly known "Copy‑Fail" mitigation applied remain vulnerable to "Dirty Frag"

Proof-of-Concept Exploit

Security researchers have published a proof‑of‑concept exploit for CVE‑2026‑43284 and CVE‑2026‑43500. The NHS England National CSOC assesses exploitation as highly likely.

Security researchers have published a proof‑of‑concept exploit for CVE‑2026‑43284 and CVE‑2026‑43500 (dubbed as "Dirty Frag") affecting Linux Kernel. When chained together, CVE‑2026‑43284 and CVE‑2026‑43500, could allow a unprivileged attacker to achieve root privileges on the Linux distribution. Note : Systems with the publicly known "Copy‑Fail" mitigation applied remain vulnerable to Dirty Frag.

Affected organisations are strongly encouraged to update affected Linux distributions' kernel package to one that includes mainline commit f4c50a4034e62ab75f1d5cdd191dd5f9c77fdff4 as soon as possible.

There are no security patches available for CVE-2026-43500.

Most major distributions are currently shipping fixed versions through normal kernel package updates.

In the Linux kernel, the following vulnerability has been resolved: xfrm: esp: avoid in-place decrypt on shared skb frags MSG_SPLICE_PAGES can attach pages from a pipe directly to an skb. TCP marks such skbs with SKBFL_SHARED_FRAG after skb_splice_from_iter(), so later paths that may modify packet data can first make a private copy. The IPv4/IPv6 datagram append paths did not set this flag when splicing pages into UDP skbs. That leaves an ESP-in-UDP packet made from shared pipe pages looking like an ordinary uncloned nonlinear skb. ESP input then takes the no-COW fast path for uncloned skbs without a frag_list and decrypts in place over data that is not owned privately by the skb. Mark IPv4/IPv6 datagram splice frags with SKBFL_SHARED_FRAG, matching TCP. Also make ESP input fall back to skb_cow_data() when the flag is present, so ESP does not decrypt externally backed frags in place. Private nonlinear skb frags still use the existing fast path. This intentionally does not change ESP output. In esp_output_head(), the path that appends the ESP trailer to existing skb tailroom without calling skb_cow_data() is not reachable for nonlinear skbs: skb_tailroom() returns zero when skb->data_len is nonzero, while ESP tailen is positive. Thus ESP output will either use the separate destination-frag path or fall back to skb_cow_data().

Last edited: 8 May 2026 1:36 pm