Bug 2521462 (CVE-2026-74659) - CVE-2026-74659 kernel: net: bridge: mrp: fix uninitialised bytes on the wire
Summary: CVE-2026-74659 kernel: net: bridge: mrp: fix uninitialised bytes on the wire
Keywords:
Status: NEW
Alias: CVE-2026-74659
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
medium
medium
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-08-22 15:46 UTC by OSIDB Bzimport
Modified: 2026-08-24 15:56 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:


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Description OSIDB Bzimport 2026-08-22 15:46:46 UTC
In the Linux kernel, the following vulnerability has been resolved:

net: bridge: mrp: fix uninitialised bytes on the wire

br_mrp_alloc_test_skb() builds MRP test frames on an skb from
dev_alloc_skb(), which does not clear the linear data area.  On the MRA
ring-role branch the sub-option TLV header is appended with

	sub_tlv = skb_put(skb, sizeof(*sub_tlv));
	sub_tlv->type = BR_MRP_SUB_TLV_HEADER_TEST_AUTO_MGR;

so sub_tlv->length is never written, and the two trailing alignment bytes
are appended with a bare skb_put() that does not clear them either.  The
neighbouring oui and sub_opt regions are explicitly zeroed, so three
uninitialised bytes are left in every MRA MRP_Test frame that goes out.

Put the sub-option TLV header and the alignment padding in a single
skb_put_zero(), which clears both.  The AUTO_MGR sub-TLV carries no
payload, so the zeroed length field is already the value it should have.


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