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High severity7.1NVD Advisory· Published Feb 27, 2025· Updated May 12, 2026

CVE-2025-21719

CVE-2025-21719

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

AI Insight

LLM-synthesized narrative grounded in this CVE's description and references.

Linux kernel ipmr crash when calling mr_mfc_uses_dev() on unres entries, causing memory corruption; patched.

Vulnerability

The Linux kernel's IP multicast routing (ipmr) code contains a bug where the function mr_mfc_uses_dev() is incorrectly called on unresolved (unres) entries. This occurs because unres entries share a union with a sk_buff_head structure, causing the function to misinterpret pointers and lead to a kernel crash. The issue was introduced and never worked as intended.

Exploitation

An attacker can trigger this vulnerability by sending specific netlink messages to dump multicast routing tables (via RTM_GETROUTE). No special privileges are required beyond network access. The crash manifests as a kernel page fault due to wild memory access, as demonstrated by syzbot.

Impact

Successful exploitation results in a denial of service (system crash). The vulnerability is rated High with a CVSS v3 score of 7.1, indicating significant availability impact.

Mitigation

Patches have been applied to the Linux kernel stable branches. The vulnerability also affects Siemens SIMATIC S7-1500 TM MFP - GNU/Linux subsystem (all versions) as per [1]. Users should apply kernel updates or follow Siemens' remediation guidance.

References
  1. SSA-265688

AI Insight generated on May 20, 2026. Synthesized from this CVE's description and the cited reference URLs; citations are validated against the source bundle.

Affected products

64

Patches

0

No patches discovered yet.

Vulnerability mechanics

AI mechanics synthesis has not run for this CVE yet.

References

11

News mentions

0

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