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CVE-2026-99121— ipv4: avoid divide by zero in fib_rebalance

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，以下漏洞已被修复： ipv4：避免在 fib_rebalance 中发生除以零的错误 fib_rebalance() 函数分两步执行：第一步计算所有符合条件的下一跳的总权重，第二步设置上限值。如果在此期间并发修改了 ignore_routes_with_linkdown 参数，可能导致第一步返回零，而第二步却检测到存在符合条件的下一跳，从而引发除以零的错误。 修复方案为：若第一步报告的总权重为零，则将每个下一跳的上限值设为 -1，并跳过除法运算。该处理方式与 commit d2c26c291

AI Predicted 7.8 Difficulty: Moderate

Possible ATT&CK Techniques 1 AI

T1069.001 · Local Groups

Affected Version Matrix 8

VendorProduct Version RangeStatus
Linux Linux 0e884c78ee19e902f300ed147083c28a0c6302f0< 5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8f affected
0e884c78ee19e902f300ed147083c28a0c6302f0< d5520e815c4b1427104ce1428ee23821f2aa824d affected
0e884c78ee19e902f300ed147083c28a0c6302f0< 5046d2880fec7d49ebed2fd2866747ee1d06ad71 affected
4.4 affected
< 4.4 unaffected
6.18.59≤ 6.18.* unaffected
7.2.13≤ 7.2.* unaffected
7.3≤ * unaffected
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I. Basic Information for CVE-2026-99121

Vulnerability Information
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Vulnerability Title
ipv4: avoid divide by zero in fib_rebalance
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: ipv4: avoid divide by zero in fib_rebalance fib_rebalance() computes the total eligible nexthop weight in one pass and programs upper bounds in a second pass. A concurrent change to ignore_routes_with_linkdown can make the first pass return zero while the second pass sees an eligible nexthop, resulting in division by zero. If the first pass reports a zero total, set each nexthop upper bound to -1 and skip the division. This matches the IPv6 fix in commit d2c26c2911dd ("ipv6: avoid divide by zero in rt6_multipath_rebalance") and preserves the lock-free rebalance path.
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 0e884c78ee19e902f300ed147083c28a0c6302f0 ~ 5dac5c7ba8f5f3fb4bf29f2a2c3cb552f5b83c8f -
Linux Linux 4.4 -

II. Public POCs for CVE-2026-99121

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III. Intelligence Information for CVE-2026-99121

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Patches & Fixes for CVE-2026-99121 (3)

Same Patch Batch · Linux · 2026-10-28 · 117 CVEs total

CVE-2026-99144 sched_ext: Fix use-after-free of a destroyed user DSQ by a deferred reenqueue
CVE-2026-99130 io_uring/cancel: don't spin on local work the task can't run
CVE-2026-99131 xfs: fix capability check in xfs
CVE-2026-99133 net/iucv: fix the recvmsg window update
CVE-2026-99132 xfs: don't hold buffer locks across sync transaction commit in xfs_sync_sb_buf
CVE-2026-99134 mac802154: fix data race and NULL deref on local->assoc_dev
CVE-2026-99135 dm-integrity: fix infinite loop on discard with large tag size
CVE-2026-99137 cifs: don't update i_size in cifs_do_truncate without a cached handle
CVE-2026-99136 dm-crypt: fix a tiny race condition in crypt_dec_pending
CVE-2026-99138 tcp: fix use-after-free in do_tcp_getsockopt(TCP_CC_INFO)
CVE-2026-99140 tracing: Fix hist trigger timestamps for buffered events
CVE-2026-99139 tcp: fix use-after-free in do_tcp_getsockopt(TCP_CONGESTION)
CVE-2026-99141 tracing: Fix crash in print_graph_function_event()
CVE-2026-99142 tracing: Check operator stack capacity before pushing
CVE-2026-99143 tracing: Keep the predicate limit separate from program capacity
CVE-2026-99156 scsi: st: Fix use-after-free race between st_remove() and st_open()
CVE-2026-99153 scsi: libiscsi: Validate the ITT reflected in a Reject PDU
CVE-2026-99152 scsi: libiscsi: Validate the task named by a management response
CVE-2026-99154 scsi: libiscsi: Reject a negative task index from parse_pdu_itt
CVE-2026-99151 drm/amd/display: Fix NULL sink dereference in USB4 bandwidth functions

Showing top 20 of 117 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux