Bug 2436768 (CVE-2026-23069)

Summary:	CVE-2026-23069 kernel: vsock/virtio: fix potential underflow in virtio_transport_get_credit()
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	emmataylor.he, rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
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Doc Text:		Story Points:	---
Clone Of:		Environment:
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Regression:	---	Mount Type:	---
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-02-04 17:02:26 UTC

In the Linux kernel, the following vulnerability has been resolved:

vsock/virtio: fix potential underflow in virtio_transport_get_credit()

The credit calculation in virtio_transport_get_credit() uses unsigned
arithmetic:

  ret = vvs->peer_buf_alloc - (vvs->tx_cnt - vvs->peer_fwd_cnt);

If the peer shrinks its advertised buffer (peer_buf_alloc) while bytes
are in flight, the subtraction can underflow and produce a large
positive value, potentially allowing more data to be queued than the
peer can handle.

Reuse virtio_transport_has_space() which already handles this case and
add a comment to make it clear why we are doing that.

[Stefano: use virtio_transport_has_space() instead of duplicating the code]
[Stefano: tweak the commit message]

Comment 1 Jon Moroney 2026-02-05 00:45:43 UTC Comment hidden (spam)

This comment was flagged as spam, view the edit history to see the original text if required.

Comment 6 Phoenix99 2026-02-25 09:24:49 UTC

(In reply to Jon Moroney from comment #1)
> Upstream advisory:
> https://lore.kernel.org/linux-cve-announce/2026020417-CVE-2026-23069-d026@gregkh/T https://cowboysafarigame.com/

Thanks for linking the upstream advisory and updating the classification. The medium severity rating seems appropriate given the potential for credit miscalculation and excessive queueing.