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CVE-2026-31680— net: ipv6: flowlabel: defer exclusive option free until RCU teardown

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.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ip6_flowlabel中独占选项在引用计数归零时过早释放，可能导致并发/proc读取时访问已释放选项状态。

CVSS 7.8 · High EPSS 0.13% · P2

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 18

VendorProduct Version RangeStatus
Linux Linux d3aedd5ebd4b0b925b0bcda548066803e1318499< 4b6798024f7b2d535f3db1002c760143cdbd1bd3 affected
d3aedd5ebd4b0b925b0bcda548066803e1318499< 3c54b66c83fb8fcbde8e6a7bf90b65856e39f827 affected
d3aedd5ebd4b0b925b0bcda548066803e1318499< 5a6b15f861b7c1304949e3350d23490a5fe429fd affected
d3aedd5ebd4b0b925b0bcda548066803e1318499< 6c7fbdb8ffde6413640de7cfbd7c976c353e89f8 affected
d3aedd5ebd4b0b925b0bcda548066803e1318499< 8027964931785cb73d520ac70a342a3dc16c249b affected
d3aedd5ebd4b0b925b0bcda548066803e1318499< 414726b69921fe6355ae453f5b35e68dd078342a affected
d3aedd5ebd4b0b925b0bcda548066803e1318499< 572ce62778519a7d4d1c15f55dd2e45a474133c4 affected
d3aedd5ebd4b0b925b0bcda548066803e1318499< 9ca562bb8e66978b53028fa32b1a190708e6a091 affected
… +10 more rows
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I. Basic Information for CVE-2026-31680

Vulnerability Information
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Vulnerability Title
net: ipv6: flowlabel: defer exclusive option free until RCU teardown
Source: CVE Program / CVE List V5
Vulnerability Description
In the Linux kernel, the following vulnerability has been resolved: net: ipv6: flowlabel: defer exclusive option free until RCU teardown `ip6fl_seq_show()` walks the global flowlabel hash under the seq-file RCU read-side lock and prints `fl->opt->opt_nflen` when an option block is present. Exclusive flowlabels currently free `fl->opt` as soon as `fl->users` drops to zero in `fl_release()`. However, the surrounding `struct ip6_flowlabel` remains visible in the global hash table until later garbage collection removes it and `fl_free_rcu()` finally tears it down. A concurrent `/proc/net/ip6_flowlabel` reader can therefore race that early `kfree()` and dereference freed option state, triggering a crash in `ip6fl_seq_show()`. Fix this by keeping `fl->opt` alive until `fl_free_rcu()`. That matches the lifetime already required for the enclosing flowlabel while readers can still reach it under RCU.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于ip6_flowlabel中独占选项在引用计数归零时过早释放，可能导致并发/proc读取时访问已释放选项状态。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux d3aedd5ebd4b0b925b0bcda548066803e1318499 ~ 4b6798024f7b2d535f3db1002c760143cdbd1bd3 -
Linux Linux 3.9 -

II. Public POCs for CVE-2026-31680

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III. Intelligence Information for CVE-2026-31680

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Same Patch Batch · Linux · 2026-04-25 · 13 CVEs total

CVE-2026-31685 9.4 CRITICAL netfilter: ip6t_eui64: reject invalid MAC header for all packets
CVE-2026-31682 9.1 CRITICAL bridge: br_nd_send: linearize skb before parsing ND options
CVE-2026-31683 7.8 HIGH batman-adv: avoid OGM aggregation when skb tailroom is insufficient
CVE-2026-31678 7.8 HIGH openvswitch: defer tunnel netdev_put to RCU release
CVE-2026-31675 7.8 HIGH net/sched: sch_netem: fix out-of-bounds access in packet corruption
CVE-2026-31673 7.8 HIGH af_unix: read UNIX_DIAG_VFS data under unix_state_lock
CVE-2026-31676 7.5 HIGH rxrpc: only handle RESPONSE during service challenge
CVE-2026-31679 7.1 HIGH openvswitch: validate MPLS set/set_masked payload length
CVE-2026-31674 7.1 HIGH netfilter: ip6t_rt: reject oversized addrnr in rt_mt6_check()
CVE-2026-31684 net: sched: act_csum: validate nested VLAN headers
CVE-2026-31681 netfilter: xt_multiport: validate range encoding in checkentry
CVE-2026-31677 crypto: af_alg - limit RX SG extraction by receive buffer budget

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2026-31680

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