CVE-2026-98049 (GCVE-0-2026-98049)

Vulnerability from cvelistv5 – Published: 2026-09-25 10:23 – Updated: 2026-09-25 10:23
VLAI
Title
bpf: zero extend the result of an arena 32-bit cmpxchg
Summary
In the Linux kernel, the following vulnerability has been resolved: bpf: zero extend the result of an arena 32-bit cmpxchg bpf_convert_ctx_accesses() rewrites an atomic on an arena pointer from BPF_STX | BPF_ATOMIC to BPF_STX | BPF_PROBE_ATOMIC, and it runs before bpf_opt_subreg_zext_lo32_rnd_hi32(). That pass emits an explicit zero extension for a 32-bit cmpxchg even when bpf_jit_needs_zext() is false. This is done because on some architectures 32-bit cmpxchg requires explicit zero extension for the dst register. E.g. on x86-64 'lock cmpxchg' does not change the %eax if comparison is successful, while BPF semantics declare that each operation on a 32-bit register zero extends it's upper half. is_cmpxchg_insn() matches BPF_MODE == BPF_ATOMIC only, so an arena cmpxchg misses said zero extension adjustment. This patch adjusts is_cmpxchg_insn() to match BPF_PROBE_ATOMIC alongside BPF_ATOMIC.
Severity
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: d503a04f8bc0c75dc9db9452d8cc79d748afb752 , < 1c1b476d43a8b6c9bc04600369dd8cc39950d98e (git)
Affected: d503a04f8bc0c75dc9db9452d8cc79d748afb752 , < 4814ed6406f3493bd554ad046da5f7fc04833571 (git)
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Linux Linux Affected: 6.10
Unaffected: 0 , < 6.10 (semver)
Unaffected: 7.2.7 , ≤ 7.2.* (semver)
Unaffected: 7.3-rc2 , ≤ * (original_commit_for_fix)
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{
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      "affected": [
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          "product": "Linux",
          "programFiles": [
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          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: zero extend the result of an arena 32-bit cmpxchg\n\nbpf_convert_ctx_accesses() rewrites an atomic on an arena pointer from\nBPF_STX | BPF_ATOMIC to BPF_STX | BPF_PROBE_ATOMIC, and it runs before\nbpf_opt_subreg_zext_lo32_rnd_hi32().\n\nThat pass emits an explicit zero extension for a 32-bit cmpxchg even\nwhen bpf_jit_needs_zext() is false. This is done because on some\narchitectures 32-bit cmpxchg requires explicit zero extension for the\ndst register. E.g. on x86-64 \u0027lock cmpxchg\u0027 does not change the %eax\nif comparison is successful, while BPF semantics declare that each\noperation on a 32-bit register zero extends it\u0027s upper half.\n\nis_cmpxchg_insn() matches BPF_MODE == BPF_ATOMIC only, so an arena\ncmpxchg misses said zero extension adjustment. This patch adjusts\nis_cmpxchg_insn() to match BPF_PROBE_ATOMIC alongside BPF_ATOMIC."
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-25T10:23:58.561Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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        },
        {
          "url": "https://git.kernel.org/stable/c/4814ed6406f3493bd554ad046da5f7fc04833571"
        }
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      "title": "bpf: zero extend the result of an arena 32-bit cmpxchg",
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    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98049",
    "datePublished": "2026-09-25T10:23:58.561Z",
    "dateReserved": "2026-09-25T10:19:56.072Z",
    "dateUpdated": "2026-09-25T10:23:58.561Z",
    "state": "PUBLISHED"
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nbpf: zero extend the result of an arena 32-bit cmpxchg\n\nbpf_convert_ctx_accesses() rewrites an atomic on an arena pointer from\nBPF_STX | BPF_ATOMIC to BPF_STX | BPF_PROBE_ATOMIC, and it runs before\nbpf_opt_subreg_zext_lo32_rnd_hi32().\n\nThat pass emits an explicit zero extension for a 32-bit cmpxchg even\nwhen bpf_jit_needs_zext() is false. This is done because on some\narchitectures 32-bit cmpxchg requires explicit zero extension for the\ndst register. E.g. on x86-64 \u0027lock cmpxchg\u0027 does not change the %eax\nif comparison is successful, while BPF semantics declare that each\noperation on a 32-bit register zero extends it\u0027s upper half.\n\nis_cmpxchg_insn() matches BPF_MODE == BPF_ATOMIC only, so an arena\ncmpxchg misses said zero extension adjustment. This patch adjusts\nis_cmpxchg_insn() to match BPF_PROBE_ATOMIC alongside BPF_ATOMIC."
          }
        ],
        "id": "CVE-2026-98049",
        "lastModified": "2026-09-25T11:17:33.770",
        "metrics": {},
        "published": "2026-09-25T11:17:33.770",
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        ],
        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
      }
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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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.
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  • 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.



Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.