# CVE-2026-98525: mctp: route: iterate socket tag list in mctp_lookup_prealloc_tag()

CVE-2026-98525 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-98525, released October 19, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-98525
- Priority: Routine
- CVSS: 6.1 (Moderate)
- EPSS: 0.0021
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Oct 18, 2026
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98525

## Description

In the Linux kernel, the following vulnerability has been resolved:  mctp: route: iterate socket tag list in mctp_lookup_prealloc_tag()  When a socket transmits a packet with MCTP_TAG_PREALLOC set, mctp_lookup_prealloc_tag() iterates over the per-netns &mns->keys list and matches netid, req_tag, peer_addr, and manual_alloc, without checking whether tmp->sk == &msk->sk. This allows any MCTP socket in the same network namespace to use and consume another socket's preallocated tag.  Iterate the socket's own tag list (&msk->keys via sklist) instead of the namespace-wide &mns->keys list in mctp_lookup_prealloc_tag(), ensuring that only tags allocated by msk are matched.  Tested in QEMU against Linux 7.3.0-rc3 by allocating a manual tag (0x18) on socket A via SIOCMCTPALLOCTAG for peer EID 9 and sending a 4-byte message with MCTP_TAG_PREALLOC from socket B in the same network namespace. On the unfixed kernel, sendto(sock_b) using socket A's preallocated tag succeeds (ret = 4); with this patch applied, sendto(sock_b) fails with -ENOENT (errno = 2) while sendto(sock_a) succeeds (ret = 4).

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 13.5 (trixie) | 6.12.113-1 | [DEBIAN-CVE-2026-98525](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98525.md) | Oct 19, 2026 |
| Linux | linux Debian 14 | 7.2.9-1 | [DEBIAN-CVE-2026-98525](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98525.md) | Oct 19, 2026 |
| Linux | linux-6.12 Debian 12.15 (bookworm) | 6.12.113-1~deb12u1 | [DEBIAN-CVE-2026-98525](https://patchblox.com/security/data/fix/linux/debian-cve-2026-98525.md) | Oct 19, 2026 |

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Data as of 2026-11-09T07:25:28Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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