CVE-2026-72057: Linux kernel · net/sched: act_ct: preserve tc_skb_cb across defragmentation
Affects Linux kernelSource CVE Database V5
Not known to be exploited · CVSS 8.2 High · fixed in fb080b6f54835d5d4d11ce3122800e6f0f6689e6 : patch Linux kernel soon.
Data as of 26 Oct 2026, 17:30 UTC
- EPSS
- 0.5% chance of exploitation in 30 days – higher than 47% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers can reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-10-16.
- Patch
- Available – fixed in fb080b6f54835d5d4d11ce3122800e6f0f6689e6, f7f45ceb855d9ba1cba594fb3f383255f7013fad, b3d835407846134b0d54637c0281b39bebef831d +5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:HExploitation evidence
Disclosed: evidence found.
CVE published 15 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade to a fixed release listed under Affected software.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| LinuxLinux | Affected
| Fixed in
|
| LinuxLinux | Affected
| Fixed in– |
Description
In the Linux kernel, the following vulnerability has been resolved: net/sched: act_ct: preserve tc_skb_cb across defragmentation tcf_ct_handle_fragments() calls nf_ct_handle_fragments() without saving and restoring skb->cb. The defrag helper clears IPCB/IP6CB, which aliases the tc_skb_cb/qdisc_skb_cb control buffer. Fragmented traffic through act_ct therefore loses qdisc metadata such as pkt_segs and can trigger WARN_ON_ONCE() in qdisc_pkt_segs() when panic_on_warn is enabled. Save and restore the full tc_skb_cb around nf_ct_handle_fragments(), matching the pattern used by ovs_ct_handle_fragments().
References
- git.kernel.org/stable/c/fb080b6f54835d5d4d11ce3122800e6f0f6689e6 (opens in a new tab)
- git.kernel.org/stable/c/67d6b00a54446c008f52cf70fc0c2ad0c712f85d (opens in a new tab)
- git.kernel.org/stable/c/2400c4b05d58834b994500a9eec90a37db44187c (opens in a new tab)
- git.kernel.org/stable/c/5c3ae5f6c7c6de73ea9b6a75154fe4ed343e1bac (opens in a new tab)
- git.kernel.org/stable/c/b3d835407846134b0d54637c0281b39bebef831d (opens in a new tab)
- git.kernel.org/stable/c/f7f45ceb855d9ba1cba594fb3f383255f7013fad (opens in a new tab)
- git.kernel.org/stable/c/9092e15defbe6c7bc241c306093ca9d358a578e7 (opens in a new tab)