UBUNTU-CVE-2026-46300
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.
02 / AFFECTED SOFTWARE
Affected packages
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03 / CONNECTIONS
Connected vulnerabilities
04 / EVIDENCE
Source records
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.
05 / REFERENCES
Further evidence
- https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=f84eca5817390257cef78013d0112481c503b4a3
- https://github.com/v12-security/pocs/tree/main/fragnesia
- https://lore.kernel.org/all/agRfuVOeMI5pbHhY@v4bel/
- https://ubuntu.com/security/CVE-2026-46300
- https://ubuntu.com/security/notices/USN-8370-1
- https://ubuntu.com/security/notices/USN-8371-1
- https://ubuntu.com/security/notices/USN-8373-1
- https://ubuntu.com/security/notices/USN-8374-1
- https://ubuntu.com/security/notices/USN-8388-1
- https://ubuntu.com/security/notices/USN-8388-2
- https://ubuntu.com/security/notices/USN-8393-1
- https://ubuntu.com/security/notices/USN-8426-1
- https://ubuntu.com/security/notices/USN-8426-2
- https://ubuntu.com/security/notices/USN-8440-1
- https://ubuntu.com/security/notices/USN-8461-1
- https://ubuntu.com/security/notices/USN-8462-1
- https://ubuntu.com/security/notices/USN-8489-1
- https://ubuntu.com/security/notices/USN-8497-1
- https://ubuntu.com/security/notices/USN-8499-1
- https://ubuntu.com/security/notices/USN-8528-1
- https://ubuntu.com/security/notices/USN-8569-1
- https://www.cve.org/CVERecord?id=CVE-2026-46300
- https://www.openwall.com/lists/oss-security/2026/05/21/11