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CVE-2021-47515 (GCVE-0-2021-47515)

Vulnerability from cvelistv5 – Published: 2024-05-24 15:09 – Updated: 2026-08-05 08:48
VLAI
Title
seg6: fix the iif in the IPv6 socket control block
Summary
In the Linux kernel, the following vulnerability has been resolved: seg6: fix the iif in the IPv6 socket control block When an IPv4 packet is received, the ip_rcv_core(...) sets the receiving interface index into the IPv4 socket control block (v5.16-rc4, net/ipv4/ip_input.c line 510): IPCB(skb)->iif = skb->skb_iif; If that IPv4 packet is meant to be encapsulated in an outer IPv6+SRH header, the seg6_do_srh_encap(...) performs the required encapsulation. In this case, the seg6_do_srh_encap function clears the IPv6 socket control block (v5.16-rc4 net/ipv6/seg6_iptunnel.c line 163): memset(IP6CB(skb), 0, sizeof(*IP6CB(skb))); The memset(...) was introduced in commit ef489749aae5 ("ipv6: sr: clear IP6CB(skb) on SRH ip4ip6 encapsulation") a long time ago (2019-01-29). Since the IPv6 socket control block and the IPv4 socket control block share the same memory area (skb->cb), the receiving interface index info is lost (IP6CB(skb)->iif is set to zero). As a side effect, that condition triggers a NULL pointer dereference if commit 0857d6f8c759 ("ipv6: When forwarding count rx stats on the orig netdev") is applied. To fix that issue, we set the IP6CB(skb)->iif with the index of the receiving interface once again.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2024-09-10 15:35 UTC
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: c630ec8bdadae9d557b1ceb9d6c06e149108a0d4 , < b16d412e5f79734033df04e97d7ea2f50a8e9fe3 (git)
Affected: 2f704348c93ff8119e642dae6a72327f90b82810 , < 6431e71093f3da586a00c6d931481ffb0dc2db0e (git)
Affected: ef489749aae508e6f17886775c075f12ff919fb1 , < ef8804e47c0a44ae106ead1740408af5ea6c6ee9 (git)
Affected: ef489749aae508e6f17886775c075f12ff919fb1 , < 666521b3852d2b2f52d570f9122b1e4b50d96831 (git)
Affected: ef489749aae508e6f17886775c075f12ff919fb1 , < 98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1 (git)
Affected: ef489749aae508e6f17886775c075f12ff919fb1 , < ae68d93354e5bf5191ee673982251864ea24dd5c (git)
Affected: b71b7e0280f47b4ac633fbfd153423814ea87810 (git)
Affected: 4.14.98 , < 4.14.258 (semver)
Affected: 4.19.20 , < 4.19.221 (semver)
Affected: 4.20.7 , < 4.21 (semver)
guessed Create a notification for this product.
Linux Linux Affected: 5.0
Unaffected: 0 , < 5.0 (semver)
Unaffected: 4.14.258 , ≤ 4.14.* (semver)
Unaffected: 4.19.221 , ≤ 4.19.* (semver)
Unaffected: 5.4.165 , ≤ 5.4.* (semver)
Unaffected: 5.10.85 , ≤ 5.10.* (semver)
Unaffected: 5.15.8 , ≤ 5.15.* (semver)
Unaffected: 5.16 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
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    "nvd": "{\"cve\":{\"id\":\"CVE-2021-47515\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2024-05-24T15:15:12.937\",\"lastModified\":\"2026-08-04T10:17:06.950\",\"vulnStatus\":\"Modified\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nseg6: fix the iif in the IPv6 socket control block\\n\\nWhen an IPv4 packet is received, the ip_rcv_core(...) sets the receiving\\ninterface index into the IPv4 socket control block (v5.16-rc4,\\nnet/ipv4/ip_input.c line 510):\\n\\n    IPCB(skb)-\u003eiif = skb-\u003eskb_iif;\\n\\nIf that IPv4 packet is meant to be encapsulated in an outer IPv6+SRH\\nheader, the seg6_do_srh_encap(...) performs the required encapsulation.\\nIn this case, the seg6_do_srh_encap function clears the IPv6 socket control\\nblock (v5.16-rc4 net/ipv6/seg6_iptunnel.c line 163):\\n\\n    memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));\\n\\nThe memset(...) was introduced in commit ef489749aae5 (\\\"ipv6: sr: clear\\nIP6CB(skb) on SRH ip4ip6 encapsulation\\\") a long time ago (2019-01-29).\\n\\nSince the IPv6 socket control block and the IPv4 socket control block share\\nthe same memory area (skb-\u003ecb), the receiving interface index info is lost\\n(IP6CB(skb)-\u003eiif is set to zero).\\n\\nAs a side effect, that condition triggers a NULL pointer dereference if\\ncommit 0857d6f8c759 (\\\"ipv6: When forwarding count rx stats on the orig\\nnetdev\\\") is applied.\\n\\nTo fix that issue, we set the IP6CB(skb)-\u003eiif with the index of the\\nreceiving interface once again.\"},{\"lang\":\"es\",\"value\":\"En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: seg6: corrige el iif en el bloque de control del socket IPv6 Cuando se recibe un paquete IPv4, ip_rcv_core(...) establece el \u00edndice de la interfaz de recepci\u00f3n en el bloque de control del socket IPv4 (v5 .16-rc4, net/ipv4/ip_input.c l\u00ednea 510): IPCB(skb)-\u0026gt;iif = skb-\u0026gt;skb_iif; Si ese paquete IPv4 debe encapsularse en un encabezado IPv6+SRH externo, seg6_do_srh_encap(...) realiza la encapsulaci\u00f3n requerida. En este caso, la funci\u00f3n seg6_do_srh_encap borra el bloque de control del socket IPv6 (v5.16-rc4 net/ipv6/seg6_iptunnel.c l\u00ednea 163): memset(IP6CB(skb), 0, sizeof(*IP6CB(skb))); El memset(...) se introdujo en El commit ef489749aae5 (\\\"ipv6: sr: clear IP6CB(skb) en la encapsulaci\u00f3n SRH ip4ip6\\\") hace mucho tiempo (29 de enero de 2019). Dado que el bloque de control del socket IPv6 y el bloque de control del socket IPv4 comparten la misma \u00e1rea de memoria (skb-\u0026gt;cb), la informaci\u00f3n del \u00edndice de la interfaz de recepci\u00f3n se pierde (IP6CB(skb)-\u0026gt;iif se establece en cero). Como efecto secundario, esa condici\u00f3n desencadena una desreferencia del puntero NULL si se aplica el commit 0857d6f8c759 (\\\"ipv6: al reenviar estad\u00edsticas de recuento de rx en el netdev original\\\"). Para solucionar ese problema, configuramos IP6CB(skb)-\u0026gt;iif con el \u00edndice de la interfaz de recepci\u00f3n una vez 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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-08-04T19:57:02+00:00",
      "cve": "CVE-2021-47515",
      "id": "CVE-2021-47515",
      "initial_release_date": "2021-01-01T00:00:00+00:00",
      "product_status:known_affected": "106",
      "product_status:known_not_affected": "92",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: seg6: fix the iif in the IPv6 socket control block",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2021/cve-2021-47515.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-09-06T17:09:19Z",
      "cve": "CVE-2021-47515",
      "id": "CVE-2021-47515",
      "initial_release_date": "2024-05-28T15:29:51Z",
      "product_status:known_affected": "479",
      "product_status:known_not_affected": "224",
      "product_status:recommended": "327",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2021-47515",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2021-47515.json",
      "version": "54"
    },
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\"unaffected\"}, {\"repo\": \"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git\", \"vendor\": \"Linux\", \"product\": \"Linux\", \"versions\": [{\"status\": \"affected\", \"version\": \"5.0\"}, {\"status\": \"unaffected\", \"version\": \"0\", \"lessThan\": \"5.0\", \"versionType\": \"semver\"}, {\"status\": \"unaffected\", \"version\": \"4.14.258\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"4.14.*\"}, {\"status\": \"unaffected\", \"version\": \"4.19.221\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"4.19.*\"}, {\"status\": \"unaffected\", \"version\": \"5.4.165\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.4.*\"}, {\"status\": \"unaffected\", \"version\": \"5.10.85\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.10.*\"}, {\"status\": \"unaffected\", \"version\": \"5.15.8\", \"versionType\": \"semver\", \"lessThanOrEqual\": \"5.15.*\"}, {\"status\": \"unaffected\", \"version\": \"5.16\", \"versionType\": \"original_commit_for_fix\", \"lessThanOrEqual\": \"*\"}], \"programFiles\": [\"net/ipv6/seg6_iptunnel.c\"], \"defaultStatus\": \"affected\"}], \"references\": [{\"url\": \"https://git.kernel.org/stable/c/b16d412e5f79734033df04e97d7ea2f50a8e9fe3\"}, {\"url\": \"https://git.kernel.org/stable/c/6431e71093f3da586a00c6d931481ffb0dc2db0e\"}, {\"url\": \"https://git.kernel.org/stable/c/ef8804e47c0a44ae106ead1740408af5ea6c6ee9\"}, {\"url\": \"https://git.kernel.org/stable/c/666521b3852d2b2f52d570f9122b1e4b50d96831\"}, {\"url\": \"https://git.kernel.org/stable/c/98adb2bbfa407c9290bda299d4c6f7a1c4ebd5e1\"}, {\"url\": \"https://git.kernel.org/stable/c/ae68d93354e5bf5191ee673982251864ea24dd5c\"}], \"x_generator\": {\"engine\": \"bippy-1.2.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"In the Linux kernel, the following vulnerability has been resolved:\\n\\nseg6: fix the iif in the IPv6 socket control block\\n\\nWhen an IPv4 packet is received, the ip_rcv_core(...) sets the receiving\\ninterface index into the IPv4 socket control block (v5.16-rc4,\\nnet/ipv4/ip_input.c line 510):\\n\\n    IPCB(skb)-\u003eiif = skb-\u003eskb_iif;\\n\\nIf that IPv4 packet is meant to be encapsulated in an outer IPv6+SRH\\nheader, the seg6_do_srh_encap(...) performs the required encapsulation.\\nIn this case, the seg6_do_srh_encap function clears the IPv6 socket control\\nblock (v5.16-rc4 net/ipv6/seg6_iptunnel.c line 163):\\n\\n    memset(IP6CB(skb), 0, sizeof(*IP6CB(skb)));\\n\\nThe memset(...) was introduced in commit ef489749aae5 (\\\"ipv6: sr: clear\\nIP6CB(skb) on SRH ip4ip6 encapsulation\\\") a long time ago (2019-01-29).\\n\\nSince the IPv6 socket control block and the IPv4 socket control block share\\nthe same memory area (skb-\u003ecb), the receiving interface index info is lost\\n(IP6CB(skb)-\u003eiif is set to zero).\\n\\nAs a side effect, that condition triggers a NULL pointer dereference if\\ncommit 0857d6f8c759 (\\\"ipv6: When forwarding count rx stats on the orig\\nnetdev\\\") is applied.\\n\\nTo fix that issue, we set the IP6CB(skb)-\u003eiif with the index of the\\nreceiving interface once again.\"}], \"cpeApplicability\": [{\"nodes\": [{\"negate\": false, \"cpeMatch\": [{\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.14.258\", \"versionStartIncluding\": \"4.14.98\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"4.19.221\", \"versionStartIncluding\": \"4.19.20\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.4.165\", \"versionStartIncluding\": \"5.0\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.10.85\", \"versionStartIncluding\": \"5.0\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.15.8\", \"versionStartIncluding\": \"5.0\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionEndExcluding\": \"5.16\", \"versionStartIncluding\": \"5.0\"}, {\"criteria\": \"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*\", \"vulnerable\": true, \"versionStartIncluding\": \"4.20.7\"}], \"operator\": \"OR\"}]}], \"providerMetadata\": {\"orgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"shortName\": \"Linux\", \"dateUpdated\": \"2026-08-05T08:48:12.387Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2021-47515\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T08:48:12.387Z\", \"dateReserved\": \"2024-05-24T15:02:54.824Z\", \"assignerOrgId\": \"416baaa9-dc9f-4396-8d5f-8c081fb06d67\", \"datePublished\": \"2024-05-24T15:09:29.334Z\", \"assignerShortName\": \"Linux\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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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.