vsock/virtio: validate packet source for connected sockets
Affects Linux kernel vsock/virtio code for connected sockets, from 4.8.0 on each branch until fixed in 5.15.224, 6.1.191, 6.6.161, 6.12.115, 6.18.59 or 7.2.13. CVSS 7.1 (high).
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Last modified
- Where the record stands: published, rejected by its publisher, or superseded by another id.What do these mean? →
- Published
- Whether CISA lists it in its Known Exploited Vulnerabilities catalog: proof that attackers are using it.What do these mean? →
- Not listed in CISA KEV
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 32/100
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Fix
- Fixed in 5.15.224, 6.1.191, 6.6.161, 6.12.115, 6.18.59, and 1 more
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
In the Linux kernel, the following vulnerability has been resolved: vsock/virtio: validate packet source for connected sockets virtio_transport_recv_pkt() looks up sockets first by the full source and destination tuple, then by destination only in the bound table. The fallback is needed for listening and connecting sockets, but sockets remain in the bound table after connect(), so it can also return a non-listening socket. The fallback does not validate the source address. In TCP_SYN_SENT, a RESPONSE from an unrelated source can transition the victim socket to TCP_ESTABLISHED while its stored remote address remains unchanged. Subsequent RW packets from that source are delivered through the same destination-only fallback. This was reproduced with capability-empty processes under different UIDs. The attacker discovered the target tuple through unprivileged AF_VSOCK sock_diag and caused the victim socket to read 16 attacker-chosen bytes; the intended peer-side socket read 0 of those 16 bytes. Add vsock_check_source() to validate the transport, source port and source CID against the peer stored in a non-listening socket. The local transport is the CID exception because its packets are generated internally with VMADDR_CID_LOCAL as their source, including connections using CID aliases. Use the helper after lock_sock() in the virtio receive path.
What to do
Check whether your setup matches what the bug needs.
Socket is non-listening and still in the bound table after connect(), so the destination-only fallback can return itUpgrade to a fixed version: 5.15.224, 6.1.191, 6.6.161, 6.12.115, 6.18.59, or one of 1 more.
Timeline
- CVE published
- First seen by cve.now3 days
- Record last updated
- Posted on X by cve.now
Affected versions
- Linux Linux
Version range not reported
- Linux Linux
4.8
- KernelLinux
From 4.8.0 · fixed in 5.15.224; From 5.16.0 · fixed in 6.1.191; From 6.2.0 · fixed in 6.6.161; From 6.7.0 · fixed in 6.12.115; From 6.13.0 · fixed in 6.18.59; From 6.19.0 · fixed in 7.2.13
Evidence 7
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Corrections
None so far.
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Questions about CVE-2026-99123
What does this mean?
A connected vsock socket can accept packets from a source other than its own peer, because the kernel does not validate the packet source for these sockets. An unrelated sender can therefore deliver 16 bytes into the socket and move it to an established state.Source: git.kernel.org
Am I affected, and how do I check?
Affected kernels are the branches listed from 4.8.0 up to their fixed releases: 5.15.224, 6.1.191, 6.6.161, 6.12.115, 6.18.59 and 7.2.13. The bug needs vsock/virtio and a non-listening socket that remains in the bound table after connect(). Check the running kernel with uname -r and whether the virtio vsock module is loaded.Source: git.kernel.org
What should I do about it?
Move to a fixed release for your branch: 5.15.224, 6.1.191, 6.6.161, 6.12.115, 6.18.59, or 7.2.13 or later. The sources give no workaround.Source: git.kernel.org
Is it being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data