Vulnerability-Lookup

GHSA-JQXW-MH4H-WM57

Vulnerability from github – Published: 2026-10-18 18:32 – Updated: 2026-10-18 18:32

Details

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

net: extend IPv6 exthdr detection of tunneled packets

Commit c4336a07eb6b ("net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback") split skb_gso_has_extension_hdr() into mutually exclusive branches on skb->encapsulation. This did not yet address all paths:

With skb->encapsulation set, the outer header is not checked. IPv6 tunnels such as ip6_gre and ip6_tunnel add an outer Destination Options header by default (encap_limit). Their GSO packets skip software GSO, then skb_csum_hwoffload_help() sees the outer extension header and calls skb_checksum_help() on the GSO skb, which warns and drops it.
Tunnels over IPv6 without an outer transport header, such as ip6_tunnel, leave skb->transport_header at the inner transport header. skb_network_header_len() then spans the outer IPv6, tunnel and inner IP headers, a false positive.
UDP tunnels without an inner network header, such as SCTP-in-UDP or PSP, have no inner IPv6 header to check. Decide on the outer header alone.
Directly dereferencing inner_ip_hdr(skb)->version without skb_header_pointer() is unsafe.

Instead, check ipv6_ext_hdr(nexthdr) on the outer IPv6 header and, if set, on the inner IPv6 header. Read the headers with skb_header_pointer(). Keep the skb_network_header_len() check when !skb->encapsulation to also catch encapsulated packets without skb->encapsulation (e.g., virtio).

Use the same helper in skb_csum_hwoffload_help(). Its open coded test has the false positive of (2) and ignores the inner header.

Background: checksum offload of tunneled packets invariants:

Non-GSO skb: - If the inner packet is CHECKSUM_PARTIAL, Local Checksum Offload computes the outer checksum in software and the device offloads only the inner L4 checksum. - If the inner packet is CHECKSUM_NONE (e.g., SCTP-in-UDP, ESP-in-UDP, Remote Checksum Offload), the device offloads the outer UDP or GRE checksum instead.

GSO skb: - A device with NETIF_F_GSO_UDP_TUNNEL_CSUM or NETIF_F_GSO_GRE_CSUM computes both inner and outer checksums per segment. The outer checksum is seeded with only the pseudo-header checksum.

A NETIF_F_IPV6_CSUM device must parse through the outer headers to reach the inner ones.

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{
  "affected": [],
  "aliases": [
    "CVE-2026-98852"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-18T16:17:39Z",
    "severity": null
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet: extend IPv6 exthdr detection of tunneled packets\n\nCommit c4336a07eb6b (\"net: correctly handle tunneled traffic on IPV6_CSUM\nGSO fallback\") split skb_gso_has_extension_hdr() into mutually exclusive\nbranches on skb-\u003eencapsulation. This did not yet address all paths:\n\n1. With skb-\u003eencapsulation set, the outer header is not checked. IPv6\n   tunnels such as ip6_gre and ip6_tunnel add an outer Destination\n   Options header by default (encap_limit). Their GSO packets skip\n   software GSO, then skb_csum_hwoffload_help() sees the outer extension\n   header and calls skb_checksum_help() on the GSO skb, which warns and\n   drops it.\n\n2. Tunnels over IPv6 without an outer transport header, such as\n   ip6_tunnel, leave skb-\u003etransport_header at the inner transport\n   header. skb_network_header_len() then spans the outer IPv6, tunnel\n   and inner IP headers, a false positive.\n\n3. UDP tunnels without an inner network header, such as SCTP-in-UDP or\n   PSP, have no inner IPv6 header to check. Decide on the outer header\n   alone.\n\n4. Directly dereferencing inner_ip_hdr(skb)-\u003eversion without\n   skb_header_pointer() is unsafe.\n\nInstead, check ipv6_ext_hdr(nexthdr) on the outer IPv6 header and, if\nset, on the inner IPv6 header. Read the headers with skb_header_pointer().\nKeep the skb_network_header_len() check when !skb-\u003eencapsulation to also\ncatch encapsulated packets without skb-\u003eencapsulation (e.g., virtio).\n\nUse the same helper in skb_csum_hwoffload_help(). Its open coded test\nhas the false positive of (2) and ignores the inner header.\n\nBackground: checksum offload of tunneled packets invariants:\n\nNon-GSO skb:\n- If the inner packet is CHECKSUM_PARTIAL, Local Checksum Offload computes\n  the outer checksum in software and the device offloads only the inner L4\n  checksum.\n- If the inner packet is CHECKSUM_NONE (e.g., SCTP-in-UDP, ESP-in-UDP,\n  Remote Checksum Offload), the device offloads the outer UDP or GRE\n  checksum instead.\n\nGSO skb:\n- A device with NETIF_F_GSO_UDP_TUNNEL_CSUM or NETIF_F_GSO_GRE_CSUM\n  computes both inner and outer checksums per segment.\n  The outer checksum is seeded with only the pseudo-header checksum.\n\nA NETIF_F_IPV6_CSUM device must parse through the outer headers to\nreach the inner ones.",
  "id": "GHSA-jqxw-mh4h-wm57",
  "modified": "2026-10-18T18:32:06Z",
  "published": "2026-10-18T18:32:06Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-98852"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/44ba9dc568c878b699d05e7cf699572dc9df4b59"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5f0764cb1c81a9712bce605d38efe6d844a70b29"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/aa480f05aed7a9eee87d4a6fc90647fe9679c670"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/cabacdf98e09eb74599c4d97d7bd7fd659598fb7"
    }
  ],
  "schema_version": "1.4.0",
  "severity": []
}

CVE-2026-98852 (GCVE-0-2026-98852)

Vulnerability from cvelistv5 – Published: 2026-10-18 15:50 – Updated: 2026-10-18 15:50

Title

net: extend IPv6 exthdr detection of tunneled packets

Summary

In the Linux kernel, the following vulnerability has been resolved: net: extend IPv6 exthdr detection of tunneled packets Commit c4336a07eb6b ("net: correctly handle tunneled traffic on IPV6_CSUM GSO fallback") split skb_gso_has_extension_hdr() into mutually exclusive branches on skb->encapsulation. This did not yet address all paths: 1. With skb->encapsulation set, the outer header is not checked. IPv6 tunnels such as ip6_gre and ip6_tunnel add an outer Destination Options header by default (encap_limit). Their GSO packets skip software GSO, then skb_csum_hwoffload_help() sees the outer extension header and calls skb_checksum_help() on the GSO skb, which warns and drops it. 2. Tunnels over IPv6 without an outer transport header, such as ip6_tunnel, leave skb->transport_header at the inner transport header. skb_network_header_len() then spans the outer IPv6, tunnel and inner IP headers, a false positive. 3. UDP tunnels without an inner network header, such as SCTP-in-UDP or PSP, have no inner IPv6 header to check. Decide on the outer header alone. 4. Directly dereferencing inner_ip_hdr(skb)->version without skb_header_pointer() is unsafe. Instead, check ipv6_ext_hdr(nexthdr) on the outer IPv6 header and, if set, on the inner IPv6 header. Read the headers with skb_header_pointer(). Keep the skb_network_header_len() check when !skb->encapsulation to also catch encapsulated packets without skb->encapsulation (e.g., virtio). Use the same helper in skb_csum_hwoffload_help(). Its open coded test has the false positive of (2) and ignores the inner header. Background: checksum offload of tunneled packets invariants: Non-GSO skb: - If the inner packet is CHECKSUM_PARTIAL, Local Checksum Offload computes the outer checksum in software and the device offloads only the inner L4 checksum. - If the inner packet is CHECKSUM_NONE (e.g., SCTP-in-UDP, ESP-in-UDP, Remote Checksum Offload), the device offloads the outer UDP or GRE checksum instead. GSO skb: - A device with NETIF_F_GSO_UDP_TUNNEL_CSUM or NETIF_F_GSO_GRE_CSUM computes both inner and outer checksums per segment. The outer checksum is seeded with only the pseudo-header checksum. A NETIF_F_IPV6_CSUM device must parse through the outer headers to reach the inner ones.

Severity

No CVSS data available.

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 7100 records in the last 180 days details

References

4 references

URL	Tags
https://git.kernel.org/stable/c/44ba9dc568c878b69…
https://git.kernel.org/stable/c/aa480f05aed7a9eee…
https://git.kernel.org/stable/c/cabacdf98e09eb745…
https://git.kernel.org/stable/c/5f0764cb1c81a9712…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 33670f780e0120c3dacda188c512bbffe0b6044c , < 44ba9dc568c878b699d05e7cf699572dc9df4b59 (git) Affected: a98b78116a27e2a57b696b569b2cb431c95cf9b6 , < aa480f05aed7a9eee87d4a6fc90647fe9679c670 (git) Affected: c4336a07eb6b2526dc2b62928b5104b41a7f81f5 , < cabacdf98e09eb74599c4d97d7bd7fd659598fb7 (git) Affected: c4336a07eb6b2526dc2b62928b5104b41a7f81f5 , < 5f0764cb1c81a9712bce605d38efe6d844a70b29 (git) Affected: 2094a7cf91b71367b649f991aacc7b579f793d0b (git) Affected: ed71cf465c75f5688b07a35d373cd1d6b589c8ea (git) Affected: 732fdeb2987c94b439d51f5cb9addddc2fc48c42 (git) Affected: 6.12.81 , < 6.12.113 (semver) Affected: 6.18.22 , < 6.18.56 (semver) Affected: 6.1.168 , < 6.2 (semver) Affected: 6.6.134 , < 6.7 (semver) Affected: 6.19.12 , < 6.20 (semver)
Linux	Linux	Affected: 7.0 Unaffected: 0 , < 7.0 (semver) Unaffected: 6.12.113 , ≤ 6.12.* (semver) Unaffected: 6.18.56 , ≤ 6.18.* (semver) Unaffected: 7.2.10 , ≤ 7.2.* (semver) Unaffected: 7.3-rc6 , ≤ * (original_commit_for_fix)

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          "versions": [
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            },
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              "status": "unaffected",
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              "status": "unaffected",
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            },
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}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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