net: bridge: mrp: fix uninitialised bytes on the wire
Key facts
- Attack vector
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- Privileges required
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- User interaction
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- Attack complexity
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- Impact type
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- Confidentiality · integrity · availability
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- Fix status
- Fixed
No CVSS vector from any source. Fix status from CNA.
Summary
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.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.15.216, 6.1.183, 6.6.152, 6.12.104, 6.18.45, 7.1.9, 7.2
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
Not affected: 5 products
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
Timeline
- 2026-10-02 Threatist record created from CVE-2026-74659
- 2026-10-03 Alias added: GHSA-j5v6-9qh5-x594
References
Other 7
- https://git.kernel.org/stable/c/014c062d23c63ec77ef2cf17a0d9363c7441cc94
- https://git.kernel.org/stable/c/7ebc23ff03668042e0b0e4034bb1518d36198d9e
- https://git.kernel.org/stable/c/06d58b8d2f053ced82e01efaeb6e7c82891eed58
- https://git.kernel.org/stable/c/a5e385eeb2d6dbbbdebfa050e67c34734ae12693
- https://git.kernel.org/stable/c/5912cf1822fbe53ae275c147868740eb384a5d3e
- https://git.kernel.org/stable/c/e08665218040f8e312abe40f74543186f3c2c941
- https://git.kernel.org/stable/c/63488dba65ef91373ef616575b32eb0eb21459f4
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Sources
- CVE-2026-74659 · CVE Program
- CVE-2026-74659 · NVD
- FIRST EPSS
- GHSA-j5v6-9qh5-x594 · GitHub Advisory Database · CC BY 4.0
- CVE-2026-74659 · Red Hat security data · CC BY 4.0
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