- 7.8HighCVSS base score
- 0.13%Exploitation in 30 daysEPSS · top 98% of all CVEs
- NoKnown exploitednot in CISA's KEV catalog
- NonePublic exploitsnone known yet
Description
In the Linux kernel, the following vulnerability has been resolved: ipv4: fix use-after-free in fib_nhc_update_mtu() fib_nhc_update_mtu() walks the nexthop exception table under RTNL, but RTNL does not serialize this walk with PMTU exception updates. The walk uses rcu_dereference_protected() with a constant true condition without holding fnhe_lock. The following interleaving can therefore occur: CPU 0 CPU 1 fib_nhc_update_mtu() update_or_create_fnhe() load fnhe spin_lock_bh(&fnhe_lock) fnhe_remove_oldest() unlink fnhe kfree_rcu(fnhe, rcu) <quiescent state> access fnhe after grace period KASAN reported: BUG: KASAN: slab-use-after-free in fib_nhc_update_mtu+0x3df/0x410 Read of size 8 at addr ffff888107d49000 by task poc/90 Call Trace: fib_nhc_update_mtu+0x3df/0x410 fib_sync_mtu+0x7a/0xd0 fib_netdev_event+0x229/0x3f0 netif_set_mtu_ext+0x33a/0x570 dev_set_mtu+0x88/0x120 The same walk updates fnhe_pmtu and fnhe_mtu_locked. These fields form a pair and other writers serialize them with fnhe_lock. RCU alone prevents reclamation, but would still allow concurrent writers to leave a mixed pair. Walk the table under RCU and acquire fnhe_lock only while updating each exception. RCU keeps the current entry alive while the short critical section serializes its paired PMTU fields. This avoids holding the global lock while scanning all 2048 buckets for every nexthop.
Timeline
ID reserved
By Linux
- 7 days later
· 7 days later
Published
- 55 days later
· 55 days later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| LinuxCNA (assigner) | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
| NVDNVD · Received | 3.1 | High7.8 | CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 0.13% · top 98% of all CVEs (11 Nov 2026)
- CISA SSVC
- Exploitation: none · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.
Affected products
- affected af7d6cce53694a88d6a1bb60c9a239a6a5144459 – < fd39e711866498ae94fcf9acf6f422a4f045b681
- affected af7d6cce53694a88d6a1bb60c9a239a6a5144459 – < e1e602d6b22d5cb1641c4459c487eb18bf569e0a
- affected af7d6cce53694a88d6a1bb60c9a239a6a5144459 – < e00f7d2b5f2540a3415a229c982af7a25ff6362e
- affected af7d6cce53694a88d6a1bb60c9a239a6a5144459 – < dfe388da13aa784851e5ebbea90afbb099075761
- affected af7d6cce53694a88d6a1bb60c9a239a6a5144459 – < 5a28a4b22dde92f9d293b94236314b8d6181dc4a
- affected af7d6cce53694a88d6a1bb60c9a239a6a5144459 – < 63996ffc594d128ccec8fc0983f91effd2d3adc4
- affected af7d6cce53694a88d6a1bb60c9a239a6a5144459 – < ed503eaad62f20cdd5122d7c3078a648a99c8f16
- affected af7d6cce53694a88d6a1bb60c9a239a6a5144459 – < bc5bde9ce3cc36502839dfe98e068f7303a50982
- affected b427832009b97a3ee412ef643a80b15372a7754d
- affected 2b7e4c735933be79882aba2bed9afa789e03c62f
- affected 8d59c3a6376bbc6dd3f7303968a719ffba75a4f1
- affected 9b4869cf385aa16f89c0f019eed4ec4e36aa441c
- affected ff34695ced21e2dfa04d0fa1c5f6c35011fa8117
- affected 3.16.62 – < 3.17
- affected 4.4.162 – < 4.5
- affected 4.9.134 – < 4.10
- affected 4.14.77 – < 4.15
- affected 4.18.15 – < 4.19
- affected 4.19
- unaffected < 4.19
- unaffected 5.10.265 – ≤ 5.10.*
- unaffected 5.15.216 – ≤ 5.15.*
- unaffected 6.1.183 – ≤ 6.1.*
- unaffected 6.6.152 – ≤ 6.6.*
- unaffected 6.12.104 – ≤ 6.12.*
- unaffected 6.18.45 – ≤ 6.18.*
- unaffected 7.1.9 – ≤ 7.1.*
- unaffected 7.2 – ≤ *
References
References8
- https://git.kernel.org/stable/c/fd39e711866498ae94fcf9acf6f422a4f045b681 (opens in a new tab)
- https://git.kernel.org/stable/c/e1e602d6b22d5cb1641c4459c487eb18bf569e0a (opens in a new tab)
- https://git.kernel.org/stable/c/e00f7d2b5f2540a3415a229c982af7a25ff6362e (opens in a new tab)
- https://git.kernel.org/stable/c/dfe388da13aa784851e5ebbea90afbb099075761 (opens in a new tab)
- https://git.kernel.org/stable/c/5a28a4b22dde92f9d293b94236314b8d6181dc4a (opens in a new tab)
- https://git.kernel.org/stable/c/63996ffc594d128ccec8fc0983f91effd2d3adc4 (opens in a new tab)
- https://git.kernel.org/stable/c/ed503eaad62f20cdd5122d7c3078a648a99c8f16 (opens in a new tab)
- https://git.kernel.org/stable/c/bc5bde9ce3cc36502839dfe98e068f7303a50982 (opens in a new tab)
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- EUVD EUVD-2026-64593 (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://cveledger.app/cve/CVE-2026-74656)Record last updated .