CVE-2026-43027: netfilter: nf_conntrack_helper: pass helper to expect cleanup
Vulnerability summary
CVE-2026-43027 is a high (CVSS 7.8) Use After Free vulnerability in linux. EPSS estimates a 0.13% chance of exploitation in the next 30 days, higher than 2.7% of scored vulnerabilities.
Not severe (CVSS 7.8, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 160 · Related 146Showing 100 of 160.
Timeline
- 01-05-2026PublishedVulnerability first disclosed.
- 15-10-2026Last modifiedVulnerability information updated.
Description
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_helper: pass helper to expect cleanup nf_conntrack_helper_unregister() calls nf_ct_expect_iterate_destroy() to remove expectations belonging to the helper being unregistered. However, it passes NULL instead of the helper pointer as the data argument, so expect_iter_me() never matches any expectation and all of them survive the cleanup. After unregister returns, nfnl_cthelper_del() frees the helper object immediately. Subsequent expectation dumps or packet-driven init_conntrack() calls then dereference the freed exp->helper, causing a use-after-free. Pass the actual helper pointer so expectations referencing it are properly destroyed before the helper object is freed. BUG: KASAN: slab-use-after-free in string+0x38f/0x430 Read of size 1 at addr ffff888003b14d20 by task poc/103 Call Trace: string+0x38f/0x430 vsnprintf+0x3cc/0x1170 seq_printf+0x17a/0x240 exp_seq_show+0x2e5/0x560 seq_read_iter+0x419/0x1280 proc_reg_read+0x1ac/0x270 vfs_read+0x179/0x930 ksys_read+0xef/0x1c0 Freed by task 103: The buggy address is located 32 bytes inside of freed 192-byte region [ffff888003b14d00, ffff888003b14dc0)
CVSS metrics
3 scores · 3 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- OSV · DebianEcosystem advisory · calculated7.8HighCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
EPSS trend
Probability
0.13%
Chance of exploitation in the next 30 days
Percentile
3%
Versus all other CVEs
30-day change
Decrease -0.05 pp
From 0.18% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu156 products
- linuxAll versions (No fix recorded) | < 5.15.0-186.196 | < 6.8.0-136.136
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 5.15.0-1112.119 | < 6.8.0-1061.64
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ ac7b848390036dadd4351899d2a23748075916bd, < 5cf28d5c8dcbbe8af6d3b145babe491906d7bad1 | ≥ ac7b848390036dadd4351899d2a23748075916bd, < 504ba4168466c91210c45acdc332479cfd5f2da6 | ≥ ac7b848390036dadd4351899d2a23748075916bd, < dc1739eff48e34cc71d4e2f03715493fbcebd8af | ≥ ac7b848390036dadd4351899d2a23748075916bd, < 2cf2737c85a2ba2b52024dafe68ffad2676f97be | ≥ ac7b848390036dadd4351899d2a23748075916bd, < 2c16e4d64dd91227742dfe196a3e7b0568bef65a | ≥ ac7b848390036dadd4351899d2a23748075916bd, < 620f3d14c1ef51d425060a3056ad8dbae8f998a3 | ≥ ac7b848390036dadd4351899d2a23748075916bd, < 90bd7e8501349db3006d21fbc09df9ffcb172965 | ≥ ac7b848390036dadd4351899d2a23748075916bd, < a242a9ae58aa46ff7dae51ce64150a93957abe65 | 4.14
- linux_kernel≥ 4.14, < 5.10.253 | ≥ 5.11, < 5.15.203 | ≥ 5.16, < 6.1.168 | ≥ 6.2, < 6.6.134 | ≥ 6.7, < 6.12.81 | ≥ 6.13, < 6.18.22 | ≥ 6.19, < 6.19.12 | 7.0:rc1 | 7.0:rc2 | 7.0:rc3 | 7.0:rc4 | 7.0:rc5 | 7.0:rc6
Debian1 product
- linux< 6.1.170-1 | < 6.12.85-1 | < 6.19.12-1
3 vendors · 159 products
