CVE-2025-38571 (GCVE-0-2025-38571)
Vulnerability from cvelistv5
Published
2025-08-19 17:02
Modified
2026-08-05 12:02
Severity ?
8.2 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: sunrpc: fix client side handling of tls alerts A security exploit was discovered in NFS over TLS in tls_alert_recv due to its assumption that there is valid data in the msghdr's iterator's kvec. Instead, this patch proposes the rework how control messages are setup and used by sock_recvmsg(). If no control message structure is setup, kTLS layer will read and process TLS data record types. As soon as it encounters a TLS control message, it would return an error. At that point, NFS can setup a kvec backed control buffer and read in the control message such as a TLS alert. Scott found that a msg iterator can advance the kvec pointer as a part of the copy process thus we need to revert the iterator before calling into the tls_alert_recv.
References
Impacted products
Vendor Product Version
Linux Linux Version: dea034b963c8901bdcc3d3880c04f0d75c95112f
Version: dea034b963c8901bdcc3d3880c04f0d75c95112f
Version: dea034b963c8901bdcc3d3880c04f0d75c95112f
Version: dea034b963c8901bdcc3d3880c04f0d75c95112f
Version: dea034b963c8901bdcc3d3880c04f0d75c95112f
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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "net/sunrpc/xprtsock.c"
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          "vendor": "Linux",
          "versions": [
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              "version": "0",
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              "version": "6.15.10",
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              "version": "6.16.1",
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            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.17",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.102",
                  "versionStartIncluding": "6.5",
                  "vulnerable": true
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                {
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                  "versionEndExcluding": "6.12.42",
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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\nsunrpc: fix client side handling of tls alerts\n\nA security exploit was discovered in NFS over TLS in tls_alert_recv\ndue to its assumption that there is valid data in the msghdr\u0027s\niterator\u0027s kvec.\n\nInstead, this patch proposes the rework how control messages are\nsetup and used by sock_recvmsg().\n\nIf no control message structure is setup, kTLS layer will read and\nprocess TLS data record types. As soon as it encounters a TLS control\nmessage, it would return an error. At that point, NFS can setup a kvec\nbacked control buffer and read in the control message such as a TLS\nalert. Scott found that a msg iterator can advance the kvec pointer\nas a part of the copy process thus we need to revert the iterator\nbefore calling into the tls_alert_recv."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.2,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The vulnerable code is the SUNRPC/NFS client\u0027s TCP-with-TLS receive path, driven entirely by records arriving from the remote RPC peer over the network. A malicious NFS server \u2014 or, with `xprtsec=tls` (anonymous TLS, `tls_client_hello_anon`), any on-path attacker impersonating it \u2014 triggers the bug purely by sending crafted RPC framing followed by a TLS alert record.\nAC:L - The attacker controls both halves of the trigger: an RPC fragment with a bogus calldir or unmatched XID forces the client into the `ITER_DISCARD` path, and an ordinary TLS alert record (even a close_notify) is then sent at will, yielding a deterministic NULL dereference with no race, no memory-layout guessing, and no reliance on victim state.\nPR:N - No credentials or privileges on the victim client are needed; the attacker acts as the TLS peer. With `xprtsec=tls` the peer is entirely unauthenticated (RFC 9289 opportunistic TLS), so even an unauthenticated MITM qualifies, and alerts are processed regardless of RPC-level authentication.\nUI:N - Exploitation needs no action from any user or administrator at attack time \u2014 the NFS-over-TLS mount is pre-existing, and the bug fires from the `xprtiod` workqueue receive path as soon as the attacker\u0027s records arrive.\nS:U - The faulting code, the corrupted read, and the resulting crash are all inside the kernel\u0027s own security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:L - On the bvec and past-the-end-kvec paths `tls_alert_recv()` reads two bytes through a type-confused or out-of-bounds pointer (a `struct page *` mistaken for `iov_base`, or an adjacent stack/heap word), leaking kernel memory into the `tls_alert_recv` tracepoint and into a fatal/non-fatal error oracle. The disclosure is real but strictly bounded to two bytes and is not returned to the attacker in bulk.\nI:N - `tls_alert_recv()` only reads through the bad pointer \u2014 there is no out-of-bounds write, no use-after-free, and no type confusion that yields a write primitive. The only effect is a bogus alert level selecting `-EACCES` versus `-EAGAIN` in the client\u0027s error handling.\nA:H - The `ITER_DISCARD` path dereferences a NULL kvec (and the exhausted-kvec path dereferences a garbage pointer read past the array), producing a kernel oops in the `xprtiod` kworker that kills the RPC receive worker and wedges all NFS I/O on that transport, or panics the machine outright where `panic_on_oops` is set."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:02:59.633Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a55b3d15331859d9fdd261cfa6d34ca2aeb0fb95"
        },
        {
          "url": "https://git.kernel.org/stable/c/c36b2fbd60e8f9c6f975522130998608880c93be"
        },
        {
          "url": "https://git.kernel.org/stable/c/3ee397eaaca4fa04db21bb98c8f1d0c6cc525368"
        },
        {
          "url": "https://git.kernel.org/stable/c/3feada5baf4dc96e151ff2ca54630e1d274e5458"
        },
        {
          "url": "https://git.kernel.org/stable/c/cc5d59081fa26506d02de2127ab822f40d88bc5a"
        }
      ],
      "title": "sunrpc: fix client side handling of tls alerts",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-38571",
    "datePublished": "2025-08-19T17:02:51.620Z",
    "dateReserved": "2025-04-16T04:51:24.025Z",
    "dateUpdated": "2026-08-05T12:02:59.633Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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