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

CVSS 7.8 · High EPSS 0.01% · P2
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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: NVD (National Vulnerability Database)
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: NVD (National Vulnerability Database)
CVSS Information
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Source: NVD (National Vulnerability Database)
Vulnerability Type
N/A
Source: NVD (National Vulnerability Database)
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

VendorProductAffected VersionsCPESubscribe
LinuxLinux d3aedd5ebd4b0b925b0bcda548066803e1318499 ~ 4b6798024f7b2d535f3db1002c760143cdbd1bd3 -
LinuxLinux 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-2026-316859.4 CRITICALnetfilter: ip6t_eui64: reject invalid MAC header for all packets
CVE-2026-316829.1 CRITICALbridge: br_nd_send: linearize skb before parsing ND options
CVE-2026-316837.8 HIGHbatman-adv: avoid OGM aggregation when skb tailroom is insufficient
CVE-2026-316787.8 HIGHopenvswitch: defer tunnel netdev_put to RCU release
CVE-2026-316757.8 HIGHnet/sched: sch_netem: fix out-of-bounds access in packet corruption
CVE-2026-316737.8 HIGHaf_unix: read UNIX_DIAG_VFS data under unix_state_lock
CVE-2026-316767.5 HIGHrxrpc: only handle RESPONSE during service challenge
CVE-2026-316797.1 HIGHopenvswitch: validate MPLS set/set_masked payload length
CVE-2026-316747.1 HIGHnetfilter: ip6t_rt: reject oversized addrnr in rt_mt6_check()
CVE-2026-31684net: sched: act_csum: validate nested VLAN headers
CVE-2026-31681netfilter: xt_multiport: validate range encoding in checkentry
CVE-2026-31677crypto: 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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