Vulnerability-Lookup

GHSA-769P-7F5G-9F2G

Vulnerability from github – Published: 2026-08-27 06:31 – Updated: 2026-08-27 06:31

Details

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

ipvs: revalidate ihl to prevent out-of-bounds access

While the outer IP header is already pulled into the skb head, we must be careful and revalidate the embedded headers after reading them from the skb frags to prevent out-of-bounds access.

One such place reported by Sashiko is ip_vs_nat_icmp() where local process can change the ihl field and after skb_ensure_writable() we can see larger value which is a problem for the ip_send_check(cih) calls.

Add check to drop the packet if the ihl field is changed.

Severity

7.8 (High)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2026-74747"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-26T15:16:53Z",
    "severity": "HIGH"
  },
  "details": "In the Linux kernel, the following vulnerability has been resolved:\n\nipvs: revalidate ihl to prevent out-of-bounds access\n\nWhile the outer IP header is already pulled into the skb head,\nwe must be careful and revalidate the embedded headers after\nreading them from the skb frags to prevent out-of-bounds\naccess.\n\nOne such place reported by Sashiko is ip_vs_nat_icmp() where\nlocal process can change the ihl field and after\nskb_ensure_writable() we can see larger value which is a\nproblem for the ip_send_check(cih) calls.\n\nAdd check to drop the packet if the ihl field is changed.",
  "id": "GHSA-769p-7f5g-9f2g",
  "modified": "2026-08-27T06:31:31Z",
  "published": "2026-08-27T06:31:31Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74747"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/5365f012451fce2453f13a568dcb72ea534c1e4d"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d93660df4dd1d116f608ada4a29a80a5d6f0a6ed"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-74747 (GCVE-0-2026-74747)

Vulnerability from cvelistv5 – Published: 2026-08-26 14:36 – Updated: 2026-08-27 05:01

Title

ipvs: revalidate ihl to prevent out-of-bounds access

Summary

In the Linux kernel, the following vulnerability has been resolved: ipvs: revalidate ihl to prevent out-of-bounds access While the outer IP header is already pulled into the skb head, we must be careful and revalidate the embedded headers after reading them from the skb frags to prevent out-of-bounds access. One such place reported by Sashiko is ip_vs_nat_icmp() where local process can change the ihl field and after skb_ensure_writable() we can see larger value which is a problem for the ip_send_check(cih) calls. Add check to drop the packet if the ihl field is changed.

Severity

7.8 (High)


                        
                          CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Assigner

Linux mitre root

References

2 references

URL	Tags
https://git.kernel.org/stable/c/5365f012451fce245…
https://git.kernel.org/stable/c/d93660df4dd1d116f…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 5365f012451fce2453f13a568dcb72ea534c1e4d (git) Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < d93660df4dd1d116f608ada4a29a80a5d6f0a6ed (git)
Linux	Linux	Affected: 2.6.12 Unaffected: 0 , < 2.6.12 (semver) Unaffected: 7.1.10 , ≤ 7.1.* (semver) Unaffected: 7.2 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/net/ip_vs.h",
            "net/netfilter/ipvs/ip_vs_core.c",
            "net/netfilter/ipvs/ip_vs_xmit.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "5365f012451fce2453f13a568dcb72ea534c1e4d",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            },
            {
              "lessThan": "d93660df4dd1d116f608ada4a29a80a5d6f0a6ed",
              "status": "affected",
              "version": "1da177e4c3f41524e886b7f1b8a0c1fc7321cac2",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "include/net/ip_vs.h",
            "net/netfilter/ipvs/ip_vs_core.c",
            "net/netfilter/ipvs/ip_vs_xmit.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "2.6.12"
            },
            {
              "lessThan": "2.6.12",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.10",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.10",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2",
                  "versionStartIncluding": "2.6.12",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipvs: revalidate ihl to prevent out-of-bounds access\n\nWhile the outer IP header is already pulled into the skb head,\nwe must be careful and revalidate the embedded headers after\nreading them from the skb frags to prevent out-of-bounds\naccess.\n\nOne such place reported by Sashiko is ip_vs_nat_icmp() where\nlocal process can change the ihl field and after\nskb_ensure_writable() we can see larger value which is a\nproblem for the ip_send_check(cih) calls.\n\nAdd check to drop the packet if the ihl field is changed."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Exploitation requires a local process to TOCTOU-modify the embedded IPv4 ihl in skb frags between ip_vs_fill_iph_skb_icmp() and skb_ensure_writable(); remote ICMP to IPVS NAT hooks reaches ip_vs_nat_icmp() but cannot change skb backing memory without local access to the packet buffer.\nAC:L - A local attacker controls both sides of the race by concurrently injecting ICMP errors matching an IPVS NAT connection and mutating the embedded header ihl in userspace-backed skb frags during softirq processing; no uncontrollable victim state or heap layout is required.\nPR:L - Only a local account able to race skb frag modification (e.g., via raw/packet sockets with CAP_NET_RAW obtainable in user namespaces) against IPVS ICMP NAT handling on a host where IPVS is already configured is needed; init-namespace root is not required.\nUI:N - No victim user interaction is required; exploitation is driven entirely by attacker-controlled local packet injection and concurrent frag modification while IPVS processes ICMP errors on NAT-mode connections through LOCAL_IN, LOCAL_OUT, or FORWARD hooks.\nS:U - The out-of-bounds access corrupts kernel skb memory on the IPVS load-balancer host within the same kernel security authority; it does not cross VM, container, or IOMMU boundaries into a separate security scope.\nC:H - After skb_ensure_writable(), ip_send_check(cih) re-reads an attacker-inflated cih-\u003eihl and ip_fast_csum() reads far beyond the validated skb region, enabling out-of-bounds kernel memory disclosure on internet-facing IPVS NAT nodes and kube-proxy IPVS clusters.\nI:H - The inflated ihl causes out-of-bounds access during ICMP NAT mangling in ip_vs_nat_icmp(), corrupting skb data beyond skb_ensure_writable()\u0027s bound; such kernel memory corruption is exploitable for control-flow hijacking and privilege escalation on load balancers.\nA:H - Out-of-bounds access in ip_send_check(cih) during ICMP NAT handling can trigger kernel oops or panic; a local attacker can repeatedly race the TOCTOU on IPVS NAT nodes, causing sustained denial of service on critical infrastructure."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-27T05:01:08.455Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/5365f012451fce2453f13a568dcb72ea534c1e4d"
        },
        {
          "url": "https://git.kernel.org/stable/c/d93660df4dd1d116f608ada4a29a80a5d6f0a6ed"
        }
      ],
      "title": "ipvs: revalidate ihl to prevent out-of-bounds access",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74747",
    "datePublished": "2026-08-26T14:36:56.563Z",
    "dateReserved": "2026-08-15T05:44:03.931Z",
    "dateUpdated": "2026-08-27T05:01:08.455Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

Detection rules are retrieved from Rulezet.

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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