EUVD-2026-39309
GHSA-3j78-pf43-6mvq
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Local-only vector confirmed by nftables configuration requirement; PR:L reflects CAP_NET_ADMIN needed; no confidentiality or integrity impact - kernel crash only.
Primary rating from NVD.
CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
5DescriptionNVD
In the Linux kernel, the following vulnerability has been resolved:
netfilter: nft_exthdr: fix register tracking for F_PRESENT flag
nft_exthdr_init() passes user-controlled priv->len to nft_parse_register_store(), which marks that many bytes in the register bitmap as initialized. However, when NFT_EXTHDR_F_PRESENT is set, the eval paths write only 1 byte (nft_reg_store8) or 4 bytes (*dest = 0 on TCP/DCCP error path). When len > 4, registers beyond the first are never written, retaining uninitialized stack data from nft_regs.
Bail out if userspace requests too much data when F_PRESENT is set.
AnalysisAI
Register tracking corruption in the Linux kernel's netfilter nft_exthdr subsystem allows a local low-privileged attacker with nftables configuration rights to trigger reads of uninitialized stack data from nft_regs, resulting in kernel instability or denial of service. The flaw affects any kernel version since the introduction of commit c078ca3b0c5b through the respective unpatched stable branches. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires local access to the target system and possession of the CAP_NET_ADMIN capability (or equivalent privilege to configure nftables rules via the nft or iptables-nft toolchain). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H, score 5.5 Medium) accurately frames this as a local, low-privilege denial-of-service requiring no user interaction. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local attacker with CAP_NET_ADMIN rights - for example, a container process with user namespace privileges - uses nft to load an nftables ruleset containing an exthdr expression with NFT_EXTHDR_F_PRESENT set and a len value greater than 4. When the kernel evaluates network packets against this rule, nft_regs registers beyond the first are read as initialized but contain uninitialized stack data, potentially corrupting downstream filter logic and causing kernel instability or a panic, resulting in a system-wide denial of service. … |
| Remediation | Upgrade to one of the vendor-released patched kernel stable branches: 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.94, 6.18.36, 7.0.13, or 7.1. … Detailed patch versions, workarounds, and compensating controls in full report. |
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Same weakness CWE-908 – Use of Uninitialized Resource
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External POC / Exploit Code
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