CVE-2026-99191 (GCVE-0-2026-99191)

Vulnerability from cvelistv5 – Published: 2026-10-28 10:35 – Updated: 2026-10-30 12:42
VLAI
Title
calipso: keep BIG TCP payload_len in calipso_skbuff_setattr()
Summary
In the Linux kernel, the following vulnerability has been resolved: calipso: keep BIG TCP payload_len in calipso_skbuff_setattr() calipso_skbuff_setattr() adjusts payload_len by the length of the option it inserts or resizes: payload = ntohs(ip6_hdr->payload_len); ip6_hdr->payload_len = htons(payload + len_delta); GRO can build BIG TCP packets larger than IPV6_MAXPLEN, and stores payload_len == 0 for them; ipv6_payload_len() then falls back to skb->len. For such a packet forwarded to a destination mapped to CALIPSO, the code above writes len_delta (or 65536 + len_delta when shrinking) into payload_len, and ipv6_payload_len() no longer falls back to skb->len. nf_tables, conntrack and sch_cake rely on it. The same arithmetic also wraps when a packet grows past IPV6_MAXPLEN, and a BIG TCP packet that shrinks below IPV6_MAXPLEN should get its real length back. Set payload_len from the skb length with ipv6_set_payload_len(), which stores 0 above IPV6_MAXPLEN and the real length otherwise, as ipv6_gro_complete() does. The network header was just reset to skb->data, so skb->len - sizeof(*ip6_hdr) is the payload length. Tested on one kernel (arm64, QEMU) with SELinux permissive, a minimal mdp-generated policy (network_peer_controls=1), "netlabelctl calipso add pass doi:16" and a NetLabel mapping of fd00:2::/64 to CALIPSO DOI 16. calipso_skbuff_setattr() was called through netlbl_skbuff_setattr() from a test-only debugfs hook (not part of this patch) adding a level-only label; payload_len after the call: case before fix after fix real length 1000, unlabeled 1016 1016 1016 70000 GSO, payload_len 0 16 0 70016 65530 GSO, grows past MAXPLEN 10 0 65546 65540 GSO with a 24 byte hop header, shrinks below MAXPLEN 65528 65532 65532 1000 with a 24 byte hop header 992 992 992 (0 means ipv6_payload_len() returns the real length.) On the forward path, with a client injecting unlabeled UDP through a router to a server, the router adds the CALIPSO option and the server delivers all datagrams (Udp6InDatagrams 5, Ip6InTruncatedPkts 0) with this patch.
Severity
No CVSS data available.
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 6846 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 81fbc812132cbc72a0f933b19bfd3a829bd946e4 , < e29d0a00c619ac794b05d64f4438204478137365 (git)
Affected: 81fbc812132cbc72a0f933b19bfd3a829bd946e4 , < 929dc8e2c9165bb651dca26b2c68067a3880406b (git)
Affected: 81fbc812132cbc72a0f933b19bfd3a829bd946e4 , < 1c9fcfca51e3c5cd46dd72a4da74d56eff183513 (git)
Affected: 81fbc812132cbc72a0f933b19bfd3a829bd946e4 , < 8ee0e03663826a76507048d58466b29321a57656 (git)
Affected: 81fbc812132cbc72a0f933b19bfd3a829bd946e4 , < 8070ed578b6b9134e045627fb745c887a806d46e (git)
guessed Create a notification for this product.
Linux Linux Affected: 5.19
Unaffected: 0 , < 5.19 (semver)
Unaffected: 6.6.161 , ≤ 6.6.* (semver)
Unaffected: 6.12.115 , ≤ 6.12.* (semver)
Unaffected: 6.18.59 , ≤ 6.18.* (semver)
Unaffected: 7.2.13 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
guessed Create a notification for this product.
Show details on NVD website
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncalipso: keep BIG TCP payload_len in calipso_skbuff_setattr()\n\ncalipso_skbuff_setattr() adjusts payload_len by the length of the\noption it inserts or resizes:\n\n\tpayload = ntohs(ip6_hdr-\u003epayload_len);\n\tip6_hdr-\u003epayload_len = htons(payload + len_delta);\n\nGRO can build BIG TCP packets larger than IPV6_MAXPLEN, and stores\npayload_len == 0 for them; ipv6_payload_len() then falls back to\nskb-\u003elen.  For such a packet forwarded to a destination mapped to\nCALIPSO, the code above writes len_delta (or 65536 + len_delta when\nshrinking) into payload_len, and ipv6_payload_len() no longer falls\nback to skb-\u003elen.  nf_tables, conntrack and sch_cake rely on it.\n\nThe same arithmetic also wraps when a packet grows past IPV6_MAXPLEN,\nand a BIG TCP packet that shrinks below IPV6_MAXPLEN should get its\nreal length back.\n\nSet payload_len from the skb length with ipv6_set_payload_len(), which\nstores 0 above IPV6_MAXPLEN and the real length otherwise, as\nipv6_gro_complete() does.  The network header was just reset to\nskb-\u003edata, so skb-\u003elen - sizeof(*ip6_hdr) is the payload length.\n\nTested on one kernel (arm64, QEMU) with SELinux permissive, a minimal\nmdp-generated policy (network_peer_controls=1), \"netlabelctl calipso\nadd pass doi:16\" and a NetLabel mapping of fd00:2::/64 to CALIPSO\nDOI 16.  calipso_skbuff_setattr() was called through\nnetlbl_skbuff_setattr() from a test-only debugfs hook (not part of\nthis patch) adding a level-only label; payload_len after the call:\n\n  case                         before fix   after fix   real length\n  1000, unlabeled                    1016        1016          1016\n  70000 GSO, payload_len 0             16           0         70016\n  65530 GSO, grows past MAXPLEN        10           0         65546\n  65540 GSO with a 24 byte hop\n  header, shrinks below MAXPLEN     65528       65532         65532\n  1000 with a 24 byte hop header      992         992           992\n\n(0 means ipv6_payload_len() returns the real length.)  On the forward\npath, with a client injecting unlabeled UDP through a router to a\nserver, the router adds the CALIPSO option and the server delivers all\ndatagrams (Udp6InDatagrams 5, Ip6InTruncatedPkts 0) with this patch."
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        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        {
          "url": "https://git.kernel.org/stable/c/8070ed578b6b9134e045627fb745c887a806d46e"
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    "state": "PUBLISHED"
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      "product_status:known_affected": "2",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "calipso: keep BIG TCP payload_len in calipso_skbuff_setattr()",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-99191.json",
      "version": "2"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ncalipso: keep BIG TCP payload_len in calipso_skbuff_setattr()\n\ncalipso_skbuff_setattr() adjusts payload_len by the length of the\noption it inserts or resizes:\n\n\tpayload = ntohs(ip6_hdr-\u003epayload_len);\n\tip6_hdr-\u003epayload_len = htons(payload + len_delta);\n\nGRO can build BIG TCP packets larger than IPV6_MAXPLEN, and stores\npayload_len == 0 for them; ipv6_payload_len() then falls back to\nskb-\u003elen.  For such a packet forwarded to a destination mapped to\nCALIPSO, the code above writes len_delta (or 65536 + len_delta when\nshrinking) into payload_len, and ipv6_payload_len() no longer falls\nback to skb-\u003elen.  nf_tables, conntrack and sch_cake rely on it.\n\nThe same arithmetic also wraps when a packet grows past IPV6_MAXPLEN,\nand a BIG TCP packet that shrinks below IPV6_MAXPLEN should get its\nreal length back.\n\nSet payload_len from the skb length with ipv6_set_payload_len(), which\nstores 0 above IPV6_MAXPLEN and the real length otherwise, as\nipv6_gro_complete() does.  The network header was just reset to\nskb-\u003edata, so skb-\u003elen - sizeof(*ip6_hdr) is the payload length.\n\nTested on one kernel (arm64, QEMU) with SELinux permissive, a minimal\nmdp-generated policy (network_peer_controls=1), \"netlabelctl calipso\nadd pass doi:16\" and a NetLabel mapping of fd00:2::/64 to CALIPSO\nDOI 16.  calipso_skbuff_setattr() was called through\nnetlbl_skbuff_setattr() from a test-only debugfs hook (not part of\nthis patch) adding a level-only label; payload_len after the call:\n\n  case                         before fix   after fix   real length\n  1000, unlabeled                    1016        1016          1016\n  70000 GSO, payload_len 0             16           0         70016\n  65530 GSO, grows past MAXPLEN        10           0         65546\n  65540 GSO with a 24 byte hop\n  header, shrinks below MAXPLEN     65528       65532         65532\n  1000 with a 24 byte hop header      992         992           992\n\n(0 means ipv6_payload_len() returns the real length.)  On the forward\npath, with a client injecting unlabeled UDP through a router to a\nserver, the router adds the CALIPSO option and the server delivers all\ndatagrams (Udp6InDatagrams 5, Ip6InTruncatedPkts 0) with this patch."
          }
        ],
        "id": "CVE-2026-99191",
        "lastModified": "2026-10-30T13:21:52.253",
        "metrics": {},
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        "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "vulnStatus": "Received"
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      "current_release_date": "2026-11-02T14:34:47+00:00",
      "cve": "CVE-2026-99191",
      "id": "CVE-2026-99191",
      "initial_release_date": "2026-10-28T10:35:47.854000+00:00",
      "product_status:known_affected": "189",
      "product_status:known_not_affected": "91",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: calipso: keep BIG TCP payload_len in calipso_skbuff_setattr()",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-99191.json",
      "version": "3"
    }
  }
}



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