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CVE-2026-99074— ipv4: stop PMTU walk when nexthop group shrinks

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

在 Linux 内核中，以下漏洞已得到修复： ipv4：当下一跳（nexthop）组缩小时，停止 PMTU 遍历 提交 7d3f3b4367f3（"net: ipv4: 若启用多路径，则为所有数据包路径缓存 PMTU"）使得 函数更新每一条路径。 对于下一跳对象， 和 会独立地加载 。RCU（Read-Copy-Update）机制保护每个组的生命周期，但无法确保两次加载操作观察到的是同一个组。如果在循环接受某个索引后，替换操作缩小了该组， 将返回 NULL，随后 会解引用该空指针，导致崩溃。 确定性探测仅扩大了真实

AI Predicted 7.8 Difficulty: Moderate EPSS 0.15% · P4

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux 3bed2abab4a682d426624ce9add9d7b6d475d4e4< 7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a affected
7f5005457b3072fe1ddf15bfef869f2a1d98e05e< c60d17d6dd61adc761ac6f65a008fefbc54cbf87 affected
7d3f3b4367f315a61fc615e3138f3d320da8c466< c6d670ac656badfd0e15355e07a13a6bdf3b69fd affected
7d3f3b4367f315a61fc615e3138f3d320da8c466< f27483f9975b5065ff67054cc7eb8edac6083488 affected
7d3f3b4367f315a61fc615e3138f3d320da8c466< 6619e01855e65ef35723685a557e3eb106f4ecf5 affected
fc07a232326a623d0be482e307c08ea7049c2846 affected
b1f7bdee5750d6cbb9497140cd6582abc5fdcb9e affected
6.6.79< 6.6.160 affected
… +10 more rows
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I. Basic Information for CVE-2026-99074

Vulnerability Information
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Vulnerability Title
ipv4: stop PMTU walk when nexthop group shrinks
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ipv4: stop PMTU walk when nexthop group shrinks Commit 7d3f3b4367f3 ("net: ipv4: Cache pmtu for all packet paths if multipath enabled") made __ip_rt_update_pmtu() update every path. For nexthop objects, fib_info_num_path() and fib_info_nhc() independently load nh->nh_grp. RCU protects each group's lifetime but does not make the loads observe the same group. If replacement shrinks the group after the loop accepts an index, fib_info_nhc() returns NULL and update_or_create_fnhe() dereferences it. A deterministic probe only widened the existing window between the real operations. On v7.2, an RTM_NEWNEXTHOP replacement published a one-member group after the PMTU reader accepted index 1 from a two-member group, producing: KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007] RIP: update_or_create_fnhe+0x45/0x15b0 Stop when the indexed path is absent. Groups are dense, so no later index exists in that snapshot. The same real-writer window completed 114,423 PMTU iterations without an oops with this check. A reproducer is available on request. Replacement requires CAP_NET_ADMIN in the network namespace. Where unprivileged user namespaces are permitted, a local user can obtain it in a new user and network namespace.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 3bed2abab4a682d426624ce9add9d7b6d475d4e4 ~ 7fd60d3c9a1e1b11ef5f1643bbae78d91eae2f4a -
Linux Linux 6.13 -

II. Public POCs for CVE-2026-99074

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III. Intelligence Information for CVE-2026-99074

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Patches & Fixes for CVE-2026-99074 (4)

Same Patch Batch · Linux · 2026-10-23 · 217 CVEs total

CVE-2026-98959 9.8 CRITICAL btrfs: fix xattr replace when multiple xattrs are packed in the same item
CVE-2026-99078 9.8 CRITICAL net/mlx5e: Prevent stale XSK buffer release on MPWQE refill retry
CVE-2026-99079 9.8 CRITICAL net/mlx5e: Prevent stale XSK buffer release on refill retry
CVE-2026-98988 8.8 HIGH namespace: keep covered mounts covered in OPEN_TREE_NAMESPACE
CVE-2026-99083 8.8 HIGH ksmbd: fix heap out-of-bounds write in krb5_authenticate()
CVE-2026-99082 8.8 HIGH KVM: x86: Use active memslots for the per-vCPU MMIO cache
CVE-2026-98981 8.8 HIGH namespace: unhash a dentry before detaching the mounts on it
CVE-2026-98980 8.8 HIGH namei: don't reveal overmounted entries in refwalk
CVE-2026-98870 8.8 HIGH ksmbd: remove stale channels from all sessions on teardown
CVE-2026-99042 8.4 HIGH io_uring/net: populate CONNECT filter fields for 24-byte sockaddr_in6
CVE-2026-98978 8.4 HIGH namespace: never expire a locked mount
CVE-2026-99064 8.1 HIGH cipso: adjust cached option offsets when removing CIPSO
CVE-2026-98968 8.1 HIGH amt: send the relay's General Query directly from the receive path
CVE-2026-99016 7.8 HIGH riscv: futex: untag the user pointer before the atomic access
CVE-2026-98999 7.8 HIGH drm/xe: Fix stale pinned_link entry when fb-pin performs the final unpin
CVE-2026-99054 7.8 HIGH tipc: destroy topsrv workqueues before closing connections
CVE-2026-99014 7.8 HIGH Bluetooth: hci_sync: Fix command skb lifetime during scan setup
CVE-2026-99053 7.8 HIGH tipc: hold a reference to nodes found by link name
CVE-2026-98945 7.8 HIGH HID: steam: Rearrange teardown sequence
CVE-2026-99051 7.8 HIGH fsverity: RCU-delay the freeing of struct fsverity_info

Showing top 20 of 217 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

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Same vendor: Linux