The Patching Friars' AlmanacA calendar of CVE saints

May 13

FragnesiaHoly card for fragnesia, generated with AI (Claude, Anthropic) for the Lunario dei Frati Patchatori.CC BY-NC-SA 4.0 # su ? Fragnesia MEMORIA FRACTA
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Saint Fragnesia, Who Forgot Whom the Fragment Belonged To

Patron of network buffers that merge, markers lost along the way, and the su command.

Life

On 13 May 2026 William Bowling and the V12 team published Fragnesia (CVE-2026-46300), a close relative of Dirty Frag. When the Linux kernel merged two packet buffers, it forgot to flag that a fragment was shared with the page cache. An in-place writer could thus modify a read-only file in memory: the demo rewrote the cached copy of the su command to get a root shell, while the on-disk file stayed intact.

Prayer

O Saint Fragnesia, who loses track of what is shared, let our buffers always remember whom they belong to. Amen.

How to celebrate

Celebrated by updating the kernel or blacklisting esp4, esp6 and rxrpc, and dropping the page cache after the fright.

Forget what is shared, and you will divide it badly.

Technical record

Disclosed on
May 13 2026
CVE
CVE-2026-46300
CVSS
7.8
Product
Linux · Linux

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.

Sources: github.com · wiz.io · github.com

Canonized during the vacant see

Related saints

Same product: Linux kernel

Same year: 2026

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