CVE-2026-74569 (GCVE-0-2026-74569)

Vulnerability from cvelistv5 – Published: 2026-08-15 12:28 – Updated: 2026-08-17 05:48
VLAI
Title
netfilter: nf_conntrack_sip: widen NAT rewrite delta to s32 in sip_help_tcp()
Summary
In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_sip: widen NAT rewrite delta to s32 in sip_help_tcp() sip_help_tcp() stores the size change of each NAT-rewritten SIP message in s16 diff and accumulates it in s16 tdiff, but a single message can grow by more than S16_MAX while the packet stays under the 65535 enlarge_skb() limit: nf_nat_sip() rewrites every matching URI, and a long Contact list expands the message by tens of kilobytes. diff then wraps, and "datalen = datalen + diff - msglen" yields a huge unsigned datalen, so the next iteration's ct_sip_get_header() reads past the linearized skb tail. Widen diff, tdiff and the seq_adjust hook to s32. Both are bounded by the 65535 byte packet limit, and the seqadj core is already s32 (nf_ct_seqadj_set() takes s32), so no previously accepted input is rejected. BUG: KASAN: use-after-free in ct_sip_get_header (net/netfilter/nf_conntrack_sip.c:464) Read of size 1 at addr ffff888010800000 by task ksoftirqd/1/25 ct_sip_get_header (net/netfilter/nf_conntrack_sip.c:464) sip_help_tcp (net/netfilter/nf_conntrack_sip.c:1694) nf_confirm (net/netfilter/nf_conntrack_proto.c:183) nf_hook_slow (net/netfilter/core.c:619) ip6_output (net/ipv6/ip6_output.c:246) ip6_forward (net/ipv6/ip6_output.c:690) ipv6_rcv (net/ipv6/ip6_input.c:351) __netif_receive_skb_one_core (net/core/dev.c:6212) process_backlog (net/core/dev.c:6676) __napi_poll (net/core/dev.c:7735) net_rx_action (net/core/dev.c:7955) handle_softirqs (kernel/softirq.c:622) run_ksoftirqd (kernel/softirq.c:1076) ...
Severity
9.8 (Critical)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: f5b321bd37fbec9188feb1f721ab46a5ac0b35da , < 63eea41759fd682229c14e0a2205802b46d106f3 (git)
Affected: f5b321bd37fbec9188feb1f721ab46a5ac0b35da , < c97621a110e386b2dd69e276eb699e1d3cec581d (git)
Affected: f5b321bd37fbec9188feb1f721ab46a5ac0b35da , < f74554e67ccf04d1fa71069e8c9afa2717e40716 (git)
Affected: f5b321bd37fbec9188feb1f721ab46a5ac0b35da , < ef5e2c6555d2bb52dfe0e4053a8c6193f9d83b64 (git)
Affected: f5b321bd37fbec9188feb1f721ab46a5ac0b35da , < db3d0e0e5d4bc5ab4fe445b9f413d1b486508ca5 (git)
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Linux Linux Affected: 2.6.34
Unaffected: 0 , < 2.6.34 (semver)
Unaffected: 6.6.151 , ≤ 6.6.* (semver)
Unaffected: 6.12.103 , ≤ 6.12.* (semver)
Unaffected: 6.18.44 , ≤ 6.18.* (semver)
Unaffected: 7.1.8 , ≤ 7.1.* (semver)
Unaffected: 7.2 , ≤ * (original_commit_for_fix)
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "include/linux/netfilter/nf_conntrack_sip.h",
            "net/netfilter/nf_conntrack_sip.c",
            "net/netfilter/nf_nat_sip.c"
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            "net/netfilter/nf_conntrack_sip.c",
            "net/netfilter/nf_nat_sip.c"
          ],
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          "vendor": "Linux",
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              "status": "unaffected",
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              "status": "unaffected",
              "version": "6.18.44",
              "versionType": "semver"
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            {
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              "status": "unaffected",
              "version": "7.1.8",
              "versionType": "semver"
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              "version": "7.2",
              "versionType": "original_commit_for_fix"
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      "cpeApplicability": [
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                  "vulnerable": true
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              "negate": false,
              "operator": "OR"
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnetfilter: nf_conntrack_sip: widen NAT rewrite delta to s32 in sip_help_tcp()\n\nsip_help_tcp() stores the size change of each NAT-rewritten SIP message\nin s16 diff and accumulates it in s16 tdiff, but a single message can\ngrow by more than S16_MAX while the packet stays under the 65535\nenlarge_skb() limit: nf_nat_sip() rewrites every matching URI, and a long\nContact list expands the message by tens of kilobytes. diff then wraps,\nand \"datalen = datalen + diff - msglen\" yields a huge unsigned datalen,\nso the next iteration\u0027s ct_sip_get_header() reads past the linearized skb\ntail.\n\nWiden diff, tdiff and the seq_adjust hook to s32. Both are bounded by the\n65535 byte packet limit, and the seqadj core is already s32\n(nf_ct_seqadj_set() takes s32), so no previously accepted input is\nrejected.\n\n  BUG: KASAN: use-after-free in ct_sip_get_header (net/netfilter/nf_conntrack_sip.c:464)\n  Read of size 1 at addr ffff888010800000 by task ksoftirqd/1/25\n   ct_sip_get_header (net/netfilter/nf_conntrack_sip.c:464)\n   sip_help_tcp (net/netfilter/nf_conntrack_sip.c:1694)\n   nf_confirm (net/netfilter/nf_conntrack_proto.c:183)\n   nf_hook_slow (net/netfilter/core.c:619)\n   ip6_output (net/ipv6/ip6_output.c:246)\n   ip6_forward (net/ipv6/ip6_output.c:690)\n   ipv6_rcv (net/ipv6/ip6_input.c:351)\n   __netif_receive_skb_one_core (net/core/dev.c:6212)\n   process_backlog (net/core/dev.c:6676)\n   __napi_poll (net/core/dev.c:7735)\n   net_rx_action (net/core/dev.c:7955)\n   handle_softirqs (kernel/softirq.c:622)\n   run_ksoftirqd (kernel/softirq.c:1076)\n   ..."
        }
      ],
      "metrics": [
        {
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            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - Remote attackers trigger sip_help_tcp() by sending crafted TCP SIP traffic that traverses netfilter nf_confirm() on POST_ROUTING/LOCAL_IN during packet receive/forward (ipv6_rcv\u2192ip6_forward\u2192ip6_output\u2192nf_hook_slow), the standard path for network-facing SIP ALG/NAT gateways.\nAC:L - Once nf_conntrack_sip and nf_nat_sip are active on a NATed SIP flow, the attacker fully controls the TCP SIP payload (Contact list length and private URIs) to force \u003e32KB NAT expansion and deterministic s16 wrap; no race or external timing is required.\nPR:N - Exploitation requires no privileges on the victim kernel; a remote SIP peer only needs to deliver malicious TCP SIP packets through an already-configured SIP conntrack/NAT helper, with no authentication or local access to the target system.\nUI:N - No victim user interaction is required beyond normal automated packet processing; the helper parses and NAT-rewrites attacker-supplied SIP data in softirq during connection tracking confirmation without any user action.\nS:U - Impact is confined to kernel netfilter/conntrack memory on the same security authority (e.g., a NAT firewall or router). This is not a VM escape, sandbox breakout, or cross-tenant boundary violation.\nC:H - Integer overflow yields a huge unsigned datalen, causing ct_sip_get_header() to read past the linearized skb tail; KASAN reports a use-after-free read, and this out-of-bounds/UAF access can disclose adjacent kernel heap memory beyond the packet buffer.\nI:H - Although the immediate fault is a read past skb bounds, KASAN-classified UAF/out-of-bounds kernel heap corruption is exploitable with heap grooming for control of freed/reallocated objects, enabling arbitrary write and potential code execution in kernel context.\nA:H - The corrupted datalen drives out-of-bounds access in softirq packet processing (ksoftirqd), which can cause kernel oops/panic and denial of service on the NAT/firewall handling the SIP flow; the bug is reliably triggerable with crafted packets."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-17T05:48:48.559Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/63eea41759fd682229c14e0a2205802b46d106f3"
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          "url": "https://git.kernel.org/stable/c/c97621a110e386b2dd69e276eb699e1d3cec581d"
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        {
          "url": "https://git.kernel.org/stable/c/db3d0e0e5d4bc5ab4fe445b9f413d1b486508ca5"
        }
      ],
      "title": "netfilter: nf_conntrack_sip: widen NAT rewrite delta to s32 in sip_help_tcp()",
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-74569",
    "datePublished": "2026-08-15T12:28:09.476Z",
    "dateReserved": "2026-08-15T05:44:03.917Z",
    "dateUpdated": "2026-08-17T05:48:48.559Z",
    "state": "PUBLISHED"
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  }
}



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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.
  • 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.