Vulnerability-Lookup

FKIE_CVE-2025-37797

Vulnerability from fkie_nvd - Published: 2025-05-02 15:15 - Updated: 2026-07-30 06:22

Severity

7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: net_sched: hfsc: Fix a UAF vulnerability in class handling This patch fixes a Use-After-Free vulnerability in the HFSC qdisc class handling. The issue occurs due to a time-of-check/time-of-use condition in hfsc_change_class() when working with certain child qdiscs like netem or codel. The vulnerability works as follows: 1. hfsc_change_class() checks if a class has packets (q.qlen != 0) 2. It then calls qdisc_peek_len(), which for certain qdiscs (e.g., codel, netem) might drop packets and empty the queue 3. The code continues assuming the queue is still non-empty, adding the class to vttree 4. This breaks HFSC scheduler assumptions that only non-empty classes are in vttree 5. Later, when the class is destroyed, this can lead to a Use-After-Free The fix adds a second queue length check after qdisc_peek_len() to verify the queue wasn't emptied.

References

URL	Tags
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/20d584a33e480ae80d105f43e0e7b56784da41b9	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/28b09a067831f7317c3841812276022d6c940677	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/39b9095dd3b55d9b2743df038c32138efa34a9de	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3aa852e3605000d5c47035c3fc3a986d14ccfa9f	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/3df275ef0a6ae181e8428a6589ef5d5231e58b5c	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/86cd4641c713455a4f1c8e54c370c598c2b1cee0	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/bb583c88d23b72d8d16453d24856c99bd93dadf5	Patch
416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/fcc8ede663569c704fb00a702973bd6c00373283	Patch
af854a3a-2127-422b-91ae-364da2661108	https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html	Mailing List, Third Party Advisory
af854a3a-2127-422b-91ae-364da2661108	https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html	Mailing List, Third Party Advisory

Impacted products

Vendor	Product	Version
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	*
linux	linux_kernel	4.14
linux	linux_kernel	4.14
linux	linux_kernel	4.14
linux	linux_kernel	4.14
linux	linux_kernel	4.14
linux	linux_kernel	4.14
linux	linux_kernel	4.14
linux	linux_kernel	4.14
linux	linux_kernel	6.15
linux	linux_kernel	6.15
linux	linux_kernel	6.15
debian	debian_linux	11.0

JSON

To clipboard

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  "descriptions": [
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      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: hfsc: Fix a UAF vulnerability in class handling\n\nThis patch fixes a Use-After-Free vulnerability in the HFSC qdisc class\nhandling. The issue occurs due to a time-of-check/time-of-use condition\nin hfsc_change_class() when working with certain child qdiscs like netem\nor codel.\n\nThe vulnerability works as follows:\n1. hfsc_change_class() checks if a class has packets (q.qlen != 0)\n2. It then calls qdisc_peek_len(), which for certain qdiscs (e.g.,\n   codel, netem) might drop packets and empty the queue\n3. The code continues assuming the queue is still non-empty, adding\n   the class to vttree\n4. This breaks HFSC scheduler assumptions that only non-empty classes\n   are in vttree\n5. Later, when the class is destroyed, this can lead to a Use-After-Free\n\nThe fix adds a second queue length check after qdisc_peek_len() to verify\nthe queue wasn\u0027t emptied."
    },
    {
      "lang": "es",
      "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: net_sched: hfsc: Se corrige una vulnerabilidad de UAF en la gesti\u00f3n de clases. Este parche corrige una vulnerabilidad de use-after-free en la gesti\u00f3n de clases de qdisc HFSC. El problema se produce debido a una condici\u00f3n de tiempo de comprobaci\u00f3n/tiempo de uso en hfsc_change_class() al trabajar con ciertas qdiscs secundarias como netem o codel. La vulnerabilidad funciona de la siguiente manera: 1. hfsc_change_class() verifica si una clase tiene paquetes (q.qlen != 0) 2. Luego llama a qdisc_peek_len(), que para ciertos qdiscs (por ejemplo, codel, netem) puede descartar paquetes y vaciar la cola 3. El c\u00f3digo contin\u00faa asumiendo que la cola todav\u00eda no est\u00e1 vac\u00eda, agregando la clase a vttree 4. Esto rompe las suposiciones del programador HFSC de que solo las clases no vac\u00edas est\u00e1n en vttree 5. M\u00e1s tarde, cuando se destruye la clase, esto puede llevar a un Use-After-Free La soluci\u00f3n agrega una segunda verificaci\u00f3n de longitud de cola despu\u00e9s de qdisc_peek_len() para verificar que la cola no se haya vaciado."
    }
  ],
  "id": "CVE-2025-37797",
  "lastModified": "2026-07-30T06:22:20.557",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
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          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
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            {
              "technicalImpact": "total"
            }
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          "role": "CISA Coordinator",
          "timestamp": "2026-06-10T20:40:32.363946Z",
          "version": "2.0.3"
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  "published": "2025-05-02T15:15:48.557",
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  "vulnStatus": "Modified",
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}

CVE-2025-37797 (GCVE-0-2025-37797)

Vulnerability from cvelistv5 – Published: 2025-05-02 14:16 – Updated: 2026-08-05 11:57

Title

net_sched: hfsc: Fix a UAF vulnerability in class handling

Summary

Severity

7.8 (High)


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

SSVC

Exploitation: none Automatable: no Technical Impact: total

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-06-10 20:40 UTC

Assigner

Linux CNA under the mitre root

CNA scorecard D 53/100 over 6667 records in the last 180 days details

References

10 references

URL	Tags
https://git.kernel.org/stable/c/28b09a067831f7317…
https://git.kernel.org/stable/c/39b9095dd3b55d9b2…
https://git.kernel.org/stable/c/fcc8ede663569c704…
https://git.kernel.org/stable/c/20d584a33e480ae80…
https://git.kernel.org/stable/c/3aa852e3605000d5c…
https://git.kernel.org/stable/c/86cd4641c713455a4…
https://git.kernel.org/stable/c/bb583c88d23b72d8d…
https://git.kernel.org/stable/c/3df275ef0a6ae181e…
https://lists.debian.org/debian-lts-announce/2025…
https://lists.debian.org/debian-lts-announce/2025…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 , < 28b09a067831f7317c3841812276022d6c940677 (git) Affected: 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 , < 39b9095dd3b55d9b2743df038c32138efa34a9de (git) Affected: 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 , < fcc8ede663569c704fb00a702973bd6c00373283 (git) Affected: 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 , < 20d584a33e480ae80d105f43e0e7b56784da41b9 (git) Affected: 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 , < 3aa852e3605000d5c47035c3fc3a986d14ccfa9f (git) Affected: 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 , < 86cd4641c713455a4f1c8e54c370c598c2b1cee0 (git) Affected: 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 , < bb583c88d23b72d8d16453d24856c99bd93dadf5 (git) Affected: 21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14 , < 3df275ef0a6ae181e8428a6589ef5d5231e58b5c (git)
Linux	Linux	Affected: 4.14 Unaffected: 0 , < 4.14 (semver) Unaffected: 5.4.293 , ≤ 5.4.* (semver) Unaffected: 5.10.237 , ≤ 5.10.* (semver) Unaffected: 5.15.181 , ≤ 5.15.* (semver) Unaffected: 6.1.136 , ≤ 6.1.* (semver) Unaffected: 6.6.89 , ≤ 6.6.* (semver) Unaffected: 6.12.26 , ≤ 6.12.* (semver) Unaffected: 6.14.5 , ≤ 6.14.* (semver) Unaffected: 6.15 , ≤ * (original_commit_for_fix)

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{
  "containers": {
    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2025-11-03T19:55:28.428Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"
          },
          {
            "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00030.html"
          }
        ],
        "title": "CVE Program Container"
      },
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2025-37797",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-06-10T20:40:32.363946Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-06-11T18:44:02.667Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sched/sch_hfsc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
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              "lessThan": "28b09a067831f7317c3841812276022d6c940677",
              "status": "affected",
              "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14",
              "versionType": "git"
            },
            {
              "lessThan": "39b9095dd3b55d9b2743df038c32138efa34a9de",
              "status": "affected",
              "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14",
              "versionType": "git"
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            {
              "lessThan": "fcc8ede663569c704fb00a702973bd6c00373283",
              "status": "affected",
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              "versionType": "git"
            },
            {
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              "versionType": "git"
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            {
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              "versionType": "git"
            },
            {
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              "versionType": "git"
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            {
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              "status": "affected",
              "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14",
              "versionType": "git"
            },
            {
              "lessThan": "3df275ef0a6ae181e8428a6589ef5d5231e58b5c",
              "status": "affected",
              "version": "21f4d5cc25ec0e6e8eb8420dd2c399e6d2fc7d14",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/sched/sch_hfsc.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.14"
            },
            {
              "lessThan": "4.14",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.4.*",
              "status": "unaffected",
              "version": "5.4.293",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.237",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.181",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.136",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.89",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.26",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.14.*",
              "status": "unaffected",
              "version": "6.14.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.15",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.4.293",
                  "versionStartIncluding": "4.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.237",
                  "versionStartIncluding": "4.14",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.181",
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                  "vulnerable": true
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                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.136",
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.89",
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.14.5",
                  "versionStartIncluding": "4.14",
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                {
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                  "vulnerable": true
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              ],
              "negate": false,
              "operator": "OR"
            }
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      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnet_sched: hfsc: Fix a UAF vulnerability in class handling\n\nThis patch fixes a Use-After-Free vulnerability in the HFSC qdisc class\nhandling. The issue occurs due to a time-of-check/time-of-use condition\nin hfsc_change_class() when working with certain child qdiscs like netem\nor codel.\n\nThe vulnerability works as follows:\n1. hfsc_change_class() checks if a class has packets (q.qlen != 0)\n2. It then calls qdisc_peek_len(), which for certain qdiscs (e.g.,\n   codel, netem) might drop packets and empty the queue\n3. The code continues assuming the queue is still non-empty, adding\n   the class to vttree\n4. This breaks HFSC scheduler assumptions that only non-empty classes\n   are in vttree\n5. Later, when the class is destroyed, this can lead to a Use-After-Free\n\nThe fix adds a second queue length check after qdisc_peek_len() to verify\nthe queue wasn\u0027t emptied."
        }
      ],
      "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 - The entire attack sequence (create hfsc qdisc, attach a codel/netem child, `tc class change`, then `tc class del`) is driven through rtnetlink RTM_NEWTCLASS/RTM_DELTCLASS messages, which require local system access. Per kernel CNA guidance, tc/netlink qdisc bugs are Local.\nAC:L - This is a deterministic time-of-check/time-of-use flaw inside a single netlink operation, not a thread race \u2014 the attacker picks the child qdisc (codel/netem) and its parameters so the peek is guaranteed to drop the packet and empty the queue. No condition outside the attacker\u0027s control is involved, and a reliable reproducer existed.\nPR:L - The tc class paths only check `netlink_ns_capable(skb, net-\u003euser_ns, CAP_NET_ADMIN)`, which an unprivileged user satisfies inside a new user+net namespace (`unshare -Urn`), where they can create a dummy/veth device, build the hfsc hierarchy and generate the traffic. Per guidance, tc/qdisc reachable via user namespaces is Low, not High.\nUI:N - The attacker performs every step \u2014 qdisc/class configuration, packet generation, class change and class deletion \u2014 with no action by any other user. Subsequent dequeue on the attacker\u0027s own device triggers the freed-object access.\nS:U - The corruption and its consequences are confined to the kernel\u0027s own memory and privilege domain; there is no crossing of a VM, IOMMU, or other security-authority boundary. Standard kernel-local privilege escalation is Unchanged.\nC:H - The freed `hfsc_class` remains linked in the parent\u0027s vt_tree/eltree, so `vttree_firstfit()`/`eltree_get_mindl()` read `cl_f`, `cl_vt`, `cl_parent` and `cl-\u003eqdisc` out of reclaimed slab memory, giving an attacker who sprays the slot a controlled read primitive and kernel memory disclosure.\nI:H - The dangling rb_node yields `rb_erase()`/`rb_insert_color()` pointer writes plus the direct `cl-\u003ecl_parent-\u003ecl_cvtmin = cl-\u003ecl_vt` write through freed memory, and `qdisc_dequeue_peeked()` makes an indirect call through `cl-\u003eqdisc-\u003eops-\u003edequeue` read from the freed object \u2014 a full write/control-flow-hijack primitive for privilege escalation.\nA:H - Even without successful exploitation, traversing and erasing rb-tree nodes inside a kfree()d `hfsc_class` reliably corrupts the scheduler tree and panics or oopses the kernel, and the attacker can repeat it at will."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T11:57:36.042Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/28b09a067831f7317c3841812276022d6c940677"
        },
        {
          "url": "https://git.kernel.org/stable/c/39b9095dd3b55d9b2743df038c32138efa34a9de"
        },
        {
          "url": "https://git.kernel.org/stable/c/fcc8ede663569c704fb00a702973bd6c00373283"
        },
        {
          "url": "https://git.kernel.org/stable/c/20d584a33e480ae80d105f43e0e7b56784da41b9"
        },
        {
          "url": "https://git.kernel.org/stable/c/3aa852e3605000d5c47035c3fc3a986d14ccfa9f"
        },
        {
          "url": "https://git.kernel.org/stable/c/86cd4641c713455a4f1c8e54c370c598c2b1cee0"
        },
        {
          "url": "https://git.kernel.org/stable/c/bb583c88d23b72d8d16453d24856c99bd93dadf5"
        },
        {
          "url": "https://git.kernel.org/stable/c/3df275ef0a6ae181e8428a6589ef5d5231e58b5c"
        }
      ],
      "title": "net_sched: hfsc: Fix a UAF vulnerability in class handling",
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        "engine": "bippy-1.2.0"
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    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-37797",
    "datePublished": "2025-05-02T14:16:01.905Z",
    "dateReserved": "2025-04-16T04:51:23.941Z",
    "dateUpdated": "2026-08-05T11:57:36.042Z",
    "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.

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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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