CVE-2026-46300

Published May 23, 2026

Last updated 10 days ago

CVSS high 7.8

Ubuntu

Container Security

Fragnesia

Overview

AI description

Automated description summarized from trusted sources.

CVE-2026-46300, dubbed "Fragnesia," is a local privilege escalation (LPE) vulnerability found in the Linux kernel's XFRM ESP-in-TCP subsystem. This flaw allows an unprivileged local attacker to perform arbitrary byte writes into the kernel page cache of read-only files. The vulnerability arises from a logic error where `skb_try_coalesce()` fails to propagate the `SKBFL_SHARED_FRAG` marker, causing the kernel to lose track of externally backed fragments. This page-cache corruption can be exploited to modify the in-memory cached copies of read-only files, such as `/usr/bin/su`, enabling an unprivileged process to gain root privileges. Fragnesia is the third LPE vulnerability discovered by William Bowling of the V12 security team in the same general area of the Linux kernel (IPsec ESP / rxrpc), following "Copy Fail" and "Dirty Frag." A public proof-of-concept exploit for CVE-2026-46300 is available.

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: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
NVD status: Modified
Products: linux_kernel

Risk scores

CVSS 3.1

Type: Primary
Base score: 7.8
Impact score: 5.9
Exploitability score: 1.8
Vector string: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Severity: HIGH

Weaknesses

nvd@nist.gov: CWE-787

Hype score: Not currently trending

Configurations

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References

Sources include official advisories and independent security research.