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Linux Kernel CVE-2026-43057

| EUVDEUVD-2026-26656 HIGH
2026-05-01 Linux
Information Disclosure Linux
7.5
CVSS 3.1 · Vendor: Linux
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Severity by source

Vendor (Linux) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SUSE
HIGH
qualitative
Red Hat
5.5 MEDIUM
qualitative

Primary rating from Vendor (Linux).

CVSS VectorVendor: Linux

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Lifecycle Timeline

7
Analysis Generated
May 03, 2026 - 07:40 vuln.today
CVSS changed
May 03, 2026 - 07:22 NVD
7.5 (HIGH)
Patch released
May 03, 2026 - 07:16 nvd
Patch available
Patch available
May 01, 2026 - 16:33 EUVD
EUVD ID Assigned
May 01, 2026 - 15:00 euvd
EUVD-2026-26656
Analysis Generated
May 01, 2026 - 15:00 vuln.today
CVE Published
May 01, 2026 - 14:15 nvd
HIGH 7.5

DescriptionCVE.org

In the Linux kernel, the following vulnerability has been resolved:

net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback

NETIF_F_IPV6_CSUM only advertises support for checksum offload of packets without IPv6 extension headers. Packets with extension headers must fall back onto software checksumming. Since TSO depends on checksum offload, those must revert to GSO.

The below commit introduces that fallback. It always checks network header length. For tunneled packets, the inner header length must be checked instead. Extend the check accordingly.

A special case is tunneled packets without inner IP protocol. Such as RFC 6951 SCTP in UDP. Those are not standard IPv6 followed by transport header either, so also must revert to the software GSO path.

AnalysisAI

A denial-of-service vulnerability in the Linux kernel's IPv6 checksum GSO fallback logic allows remote unauthenticated attackers to trigger system instability via specially crafted tunneled IPv6 packets with extension headers. The flaw affects network packet processing when NETIF_F_IPV6_CSUM offload is enabled, causing incorrect handling of tunneled traffic that requires software checksumming. EPSS score is low (0.02%, 7th percentile), indicating minimal observed exploitation activity. Vendor-released patches are available across multiple kernel version branches (6.1.168, 6.6.134, 6.12.81, 6.18.22, 6.19.12, 7.0), confirmed by upstream Linux kernel commits. No public exploit identified at time of analysis, though CVSS vector indicates straightforward network-based exploitation (AV:N/AC:L/PR:N/UI:N).

Technical ContextAI

This vulnerability resides in the Linux kernel's network stack GSO (Generic Segmentation Offload) implementation for IPv6. The NETIF_F_IPV6_CSUM feature flag advertises hardware checksum offload capability for standard IPv6 packets without extension headers. When IPv6 packets contain extension headers (like hop-by-hop options, routing headers, or fragmentation headers), the kernel must fall back to software checksumming, which in turn requires reverting from TSO (TCP Segmentation Offload) to GSO. The vulnerable code path incorrectly checks the outer network header length for tunneled packets (such as IPv6-in-IPv6, GRE, or VXLAN encapsulation) when it should inspect the inner header. This mismatch causes incorrect checksum handling for tunneled traffic. Edge cases like RFC 6951 SCTP-over-UDP tunneling, which lack a standard inner IP protocol, further complicate the logic. The affected CPE strings indicate widespread impact across Linux kernel versions, though EUVD data suggests fixes target specific commit ranges introduced around kernel 6.1 through 6.17+ development cycles.

RemediationAI

Apply vendor-released kernel updates immediately for systems processing tunneled IPv6 traffic. Upgrade to patched versions: Linux kernel 6.1.168+ for 6.1.x branch, 6.6.134+ for 6.6.x branch, 6.12.81+ for 6.12.x branch, 6.18.22+ for 6.18.x branch, 6.19.12+ for 6.19.x branch, or mainline 7.0+. Distribution-specific patches are available through standard package managers (yum, apt, zypper). Upstream fix commits can be reviewed at https://git.kernel.org/stable/c/2094a7cf91b71367b649f991aacc7b579f793d0b and related stable branch commits. For systems unable to patch immediately, implement compensating controls by disabling IPv6 tunnel interfaces (ip link set <tunnel-interface> down) if tunneling is not operationally required, though this breaks tunnel-dependent network paths. Alternatively, disable NETIF_F_IPV6_CSUM offload via ethtool (ethtool -K <interface> tx-checksum-ipv6 off) to force all IPv6 traffic through software checksum paths, which incurs CPU overhead of 5-15% depending on network throughput but eliminates the vulnerable code path. Monitor kernel logs (dmesg) for IPv6 GSO-related warnings or network stack panics as indicators of exploitation attempts. Test patches in staging environments first, as network stack changes can affect performance or compatibility with specialized NICs (Mellanox, Broadcom) or SR-IOV configurations.

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Vendor StatusVendor

SUSE

Severity: High
Product Status
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise Desktop 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Availability Extension 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP7 Fixed

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CVE-2026-43057 vulnerability details – vuln.today
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