Bug 2537747 (CVE-2026-95507)

Summary: CVE-2026-95507 libslirp: libslirp: out-of-bounds read in NC-SI OEM response handler discloses host memory to guest
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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An out-of-bounds read was found in the NC-SI OEM response handler of libslirp. A truncated NC-SI OEM Ethernet frame causes ncsi_rsp_handler_oem() to read up to 4 bytes beyond the supplied packet length and reflect the value into the response sent to the guest, resulting in guest-observable disclosure of adjacent host process memory.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Bug Depends On: 2537752    
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Description OSIDB Bzimport 2026-09-22 07:26:16 UTC 
A flaw was found in libslirp. The NC-SI OEM response handler (ncsi_rsp_handler_oem() in src/ncsi.c) reads and reflects the 4-byte mfr_id field from the incoming NC-SI OEM command packet into the outgoing response before validating that the packet is large enough to contain that field. ncsi_input() only validates pkt_len against the 16-byte NC-SI common header (the fix scope of CVE-2020-29129), leaving the OEM sub-dispatch path, added afterward, unchecked. A guest capable of sending a crafted 30-33 byte NC-SI OEM Ethernet frame (ethertype 0x88F8) can cause up to 4 bytes of adjacent host RX-buffer memory to be disclosed back to the guest in the NC-SI response; if the instance is configured with a Mellanox manufacturer ID, a second handler (ncsi_rsp_handler_oem_mlx()) similarly over-reads up to 4 additional bytes from cmd->data. This is a guest-triggerable, bounded host memory disclosure; there is no write and no code execution.