CVE-2026-23455 (GCVE-0-2026-23455)

Vulnerability from cvelistv5 – Published: 2026-04-03 15:15 – Updated: 2026-09-08 08:46
VLAI
Title
netfilter: nf_conntrack_h323: check for zero length in DecodeQ931()
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_h323: check for zero length in DecodeQ931() In DecodeQ931(), the UserUserIE code path reads a 16-bit length from the packet, then decrements it by 1 to skip the protocol discriminator byte before passing it to DecodeH323_UserInformation(). If the encoded length is 0, the decrement wraps to -1, which is then passed as a large value to the decoder, leading to an out-of-bounds read. Add a check to ensure len is positive after the decrement.
Severity
9.1 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 5e35941d990123f155b02d5663e51a24f816b6f3 , < 2121f5fbe88daff0f1fc5bc47d359426c74b86b0 (git)
Affected: 5e35941d990123f155b02d5663e51a24f816b6f3 , < 65fa92f79677858b14b9e4b7275f26639afe2710 (git)
Affected: 5e35941d990123f155b02d5663e51a24f816b6f3 , < 495e97af9e7249ee02b72bb1d0848a6efc3700f4 (git)
Affected: 5e35941d990123f155b02d5663e51a24f816b6f3 , < f5e4f4e4cdb75ec36802059a94195a31f193da60 (git)
Affected: 5e35941d990123f155b02d5663e51a24f816b6f3 , < 633e8f87dad32263f6a57dccdb873f042c062111 (git)
Affected: 5e35941d990123f155b02d5663e51a24f816b6f3 , < 9d00fe7d6d7c5b5f1065a6e042b54f2e44bd6df8 (git)
Affected: 5e35941d990123f155b02d5663e51a24f816b6f3 , < b652b05d51003ac074b912684f9ec7486231717b (git)
Affected: 5e35941d990123f155b02d5663e51a24f816b6f3 , < f173d0f4c0f689173f8cdac79991043a4a89bf66 (git)
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Linux Linux Affected: 2.6.17
Unaffected: 0 , < 2.6.17 (semver)
Unaffected: 5.10.253 , ≤ 5.10.* (semver)
Unaffected: 5.15.203 , ≤ 5.15.* (semver)
Unaffected: 6.1.167 , ≤ 6.1.* (semver)
Unaffected: 6.6.130 , ≤ 6.6.* (semver)
Unaffected: 6.12.78 , ≤ 6.12.* (semver)
Unaffected: 6.18.20 , ≤ 6.18.* (semver)
Unaffected: 6.19.10 , ≤ 6.19.* (semver)
Unaffected: 7.0 , ≤ * (original_commit_for_fix)
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Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
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Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.6 , < * (custom)
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Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP Affected: V3.1.5 , < * (custom)
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        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_h323: check for zero length in DecodeQ931()\n\nIn DecodeQ931(), the UserUserIE code path reads a 16-bit length from\nthe packet, then decrements it by 1 to skip the protocol discriminator\nbyte before passing it to DecodeH323_UserInformation(). If the encoded\nlength is 0, the decrement wraps to -1, which is then passed as a\nlarge value to the decoder, leading to an out-of-bounds read.\n\nAdd a check to ensure len is positive after the decrement."
          },
          {
            "lang": "es",
            "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nnetfilter: nf_conntrack_h323: comprobaci\u00f3n de longitud cero en DecodeQ931()\n\nEn DecodeQ931(), la ruta de c\u00f3digo UserUserIE lee una longitud de 16 bits del paquete, luego la decrementa en 1 para omitir el byte discriminador del protocolo antes de pasarla a DecodeH323_UserInformation(). Si la longitud codificada es 0, el decremento se ajusta a -1, que luego se pasa como un valor grande al decodificador, lo que lleva a una lectura fuera de l\u00edmites.\n\nSe a\u00f1ade una comprobaci\u00f3n para asegurar que \u0027len\u0027 sea positivo despu\u00e9s del decremento."
          }
        ],
        "id": "CVE-2026-23455",
        "lastModified": "2026-07-24T22:10:00.140",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 9.1,
                "baseSeverity": "CRITICAL",
                "confidentialityImpact": "HIGH",
                "integrityImpact": "NONE",
                "privilegesRequired": "NONE",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
                "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H",
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            "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
            "tags": [
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        "vulnStatus": "Modified",
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          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-125"
              }
            ],
            "source": "nvd@nist.gov",
            "type": "Primary"
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    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-17T10:07:37+00:00",
      "cve": "CVE-2026-23455",
      "id": "CVE-2026-23455",
      "initial_release_date": "2026-04-03T00:00:00+00:00",
      "product_status:fixed": "2085",
      "product_status:known_affected": "36",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: netfilter: nf_conntrack_h323: check for zero length in DecodeQ931()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-23455.json",
      "version": "3"
    }
  }
}



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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

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.


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.