Xircom, Inc. — 3 prefixes (MA-L)

A MAC address beginning 00:05:3C, 00:10:A4, or 00:80:C7 identifies hardware from Xircom, Inc., a laptop networking-adapter maker active from 1988 through its 2001 acquisition by Intel. These prefixes typically turn up on PCMCIA and CardBus Ethernet or modem cards built for 1990s and early-2000s notebook computers.

Xircom was a real, SEC-reporting public company (CIK 0000883905), founded in 1988 by Dirk Gates and Kirk Mathews and headquartered in Thousand Oaks, California, with a second registered address in Calabasas. At its peak it employed roughly 2,000 people, generated around $500 million in annual revenue, and carried a market capitalization above $2 billion.

Its product line centered on PC-card networking: the Pocket LAN Adapter, CreditCard Ethernet Adapter, and combo RealPort Ethernet-plus-modem-plus-GSM cards, alongside the REX 6000 pocket PDA. Intel announced its acquisition of Xircom on 2001-01-15 for roughly $748 million in an all-cash tender offer at $25 per share, and wound the Thousand Oaks operation down by early 2003.

Two CVEs touch Xircom hardware indirectly rather than the OUI itself: CVE-2023-1670, a use-after-free in the Linux kernel's Xircom PCMCIA Ethernet driver (CVSS 7.8, published 2023-03-30), and CVE-2001-1520, a cleartext-PIN disclosure flaw in the REX 6000 PDA. As of an August 2026 search, no malware or spoofing association is recorded against the 00:05:3C, 00:10:A4, or 00:80:C7 ranges themselves.

Vendor

Xircom, Inc., Thousand Oaks / Calabasas, CA, US — the IEEE MA-L registry

Device class

PCMCIA/CardBus laptop Ethernet and modem network adapters; also the REX 6000 pocket PDA — https://en.wikipedia.org/wiki/Xircom

OUI blocks

00:05:3C, 00:10:A4, 00:80:C7 — three standalone MA-L /24 assignments, not a shared IEEE base — the IEEE MA-L registry

Company status

Defunct — acquired by Intel Corporation, 2001-01-15, ~$748M all-cash tender offer — https://www.intel.com/pressroom/archive/releases/2001/20010115corp.htm

Also seen on

Linux kernel PCMCIA drivers (xircom_cb, xircom_tulip_cb) written to support these adapter families

IEEE assignment

3 prefixes (00:05:3C, 00:10:A4, 00:80:C7) → XIRCOM [Confirmed] — the IEEE MA-L registry

Registry / block size

MA-L (24-bit OUI) × 3; no MA-M or MA-S assignments found in the cached registries [Confirmed] — the IEEE MA-L registry, the IEEE MA-M registry, the IEEE MA-S registry

HQ / country

2300 Corporate Center Dr., Thousand Oaks, CA 91320, US (00:05:3C, 00:10:A4); 26025 Mureau Road, Calabasas, CA 91302, US (00:80:C7) [Confirmed] — the IEEE MA-L registry

Company status

Defunct — acquired by Intel Corporation, effective 2001-01-15 [Confirmed] — https://www.intel.com/pressroom/archive/releases/2001/20010115corp.htm

Device types

PCMCIA/CardBus Ethernet adapter, PCMCIA/CardBus modem adapter, pocket PDA (REX 6000) [Confirmed] — https://en.wikipedia.org/wiki/Xircom

Notable products

Pocket LAN Adapter, CreditCard Ethernet Adapter, RealPort combo Ethernet/modem/GSM card, REX 6000 PDA [Confirmed] — https://en.wikipedia.org/wiki/Xircom

Verified sample prefixes (all MA-L, XIRCOM)

00:05:3C, 00:10:A4, 00:80:C7 [Confirmed] — the IEEE MA-L registry

Independent corroboration

00:80:C7 registrant name and address matched on a third-party OUI mirror (macvendorlookup.com) [Likely] — third-party mirror, not IEEE-primary

Security note

CVE-2023-1670, use-after-free in the Linux kernel's Xircom PCMCIA Ethernet driver, CVSS 7.8, published 2023-03-30 [Confirmed] — https://ubuntu.com/security/CVE-2023-1670

Security note

CVE-2001-1520, cleartext-PIN disclosure in the Xircom REX 6000 PDA [Confirmed] — https://cxsecurity.com/cveproduct/327/1728/xircom_rex__36__30__30__30_/

Registration date

Unknown — IEEE's public OUI data (the IEEE MA-L registry: Registry, Assignment, Organization Name, Organization Address) carries no assignment/registration date [Confirmed] — the IEEE MA-L registry

Related vendors

none identified [Unknown]

Analyst note

three standalone, company-owned MA-L blocks (not a shared IEEE base like 70:B3:D5); Xircom hardware has been out of production since the 2001 Intel acquisition, so these prefixes most likely reflect legacy inventory or collector equipment today rather than an active product line.