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Proof-of-Concept Exploit Released for Three Vulnerabilities in the Linux Kernel

Successful exploitation of CVE-2026-46300, CVE‑2026‑43284, and CVE‑2026‑43500 in Linux distributions could allow an unprivileged attacker to achieve root privileges on the system

Threat ID:
CC-4779
Threat Severity:
Medium
Published:
8 May 2026 1:36 PM
Report a cyber attack: call 0300 303 5222 or email [email protected]

Summary

Successful exploitation of CVE-2026-46300, CVE‑2026‑43284, and CVE‑2026‑43500 in Linux distributions could allow an unprivileged attacker to achieve root privileges on the system

Threat details

Proof-of-Concept Exploit

Security researchers have published a proof‑of‑concept exploit for CVE-2026-46300, CVE‑2026‑43284, and CVE‑2026‑43500. The NHS England National CSOC assesses exploitation as highly likely. 

Introduction

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, successful exploitation of CVE‑2026‑43284 and CVE‑2026‑43500, could allow an 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.

CVE-2026-46300 (dubbed as "Fragnesia")

Security researchers have published a proof‑of‑concept exploit for CVE-2026-46300 (dubbed as "Fragnesia"). CVE-2026-46300 is a member of the Dirty Frag vulnerability class affecting Linux Kernel. Successful exploitation could allow a local, unprivileged attacker to gain root access on Linux systems via kernel page‑cache corruption. 

Note: Linux kernel versions vulnerable to the “Dirty Frag” are also vulnerable to "Fragnesia", including kernels released prior to 13 May 2026.

Threat updates

Date Update
14 May 2026 CVE-2026-46300 ("dubbed as Fragnesia") published

Affected platform updated to reflect systems vulnerable to "Fragnesia"

Added a blue box for CVE-2026-46300 

Remediation updated to reflect mitigations for CVE-2026-46300
11 May 2026 CVE-2026-43500 record published

Security patches published for CVE-2026-43500

Remediation advice

Affected organisations are strongly encouraged to update affected Linux distributions' kernel package to one that includes mainline commit f4c50a4034e62ab75f1d5cdd191dd5f9c77fdff4  and aa54b1d27fe0c2b78e664a34fd0fdf7cd1960d71 as soon as possible.

The two mainline commits mitigate risks to both Dirty Frag and Fragnesia vulnerabilities. 

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

CVE Vulnerabilities

Status Published

CVE-2026-43284

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().
Status Published

CVE-2026-43500

In the Linux kernel, the following vulnerability has been resolved: rxrpc: Also unshare DATA/RESPONSE packets when paged frags are present The DATA-packet handler in rxrpc_input_call_event() and the RESPONSE handler in rxrpc_verify_response() copy the skb to a linear one before calling into the security ops only when skb_cloned() is true. An skb that is not cloned but still carries externally-owned paged fragments (e.g. SKBFL_SHARED_FRAG set by splice() into a UDP socket via __ip_append_data, or a chained skb_has_frag_list()) falls through to the in-place decryption path, which binds the frag pages directly into the AEAD/skcipher SGL via skb_to_sgvec(). Extend the gate to also unshare when skb_has_frag_list() or skb_has_shared_frag() is true. This catches the splice-loopback vector and other externally-shared frag sources while preserving the zero-copy fast path for skbs whose frags are kernel-private (e.g. NIC page_pool RX, GRO). The OOM/trace handling already in place is reused.
Status Reserved

CVE-2026-46300

Last edited: 14 May 2026 2:04 pm