CVE-2025-40176 (GCVE-0-2025-40176)

Vulnerability from cvelistv5 – Published: 2025-11-12 10:53 – Updated: 2026-08-05 12:08
VLAI
Title
tls: wait for pending async decryptions if tls_strp_msg_hold fails
Summary
In the Linux kernel, the following vulnerability has been resolved: tls: wait for pending async decryptions if tls_strp_msg_hold fails Async decryption calls tls_strp_msg_hold to create a clone of the input skb to hold references to the memory it uses. If we fail to allocate that clone, proceeding with async decryption can lead to various issues (UAF on the skb, writing into userspace memory after the recv() call has returned). In this case, wait for all pending decryption requests.
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
Linux Linux Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 9f83fd0c179e0f458e824e417f9d5ad53443f685 (git)
Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < c61d4368197d65c4809d9271f3b85325a600586a (git)
Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 39dec4ea3daf77f684308576baf483b55ca7f160 (git)
Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < 4fc109d0ab196bd943b7451276690fb6bb48c2e0 (git)
Affected: 84c61fe1a75b4255df1e1e7c054c9e6d048da417 , < b8a6ff84abbcbbc445463de58704686011edc8e1 (git)
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Linux Linux Affected: 6.0
Unaffected: 0 , < 6.0 (semver)
Unaffected: 6.1.158 , ≤ 6.1.* (semver)
Unaffected: 6.6.114 , ≤ 6.6.* (semver)
Unaffected: 6.12.55 , ≤ 6.12.* (semver)
Unaffected: 6.17.5 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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{
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          "programFiles": [
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          "product": "Linux",
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          "vendor": "Linux",
          "versions": [
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              "version": "0",
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              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.6.114",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.12.55",
              "versionType": "semver"
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              "status": "unaffected",
              "version": "6.17.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "6.18",
              "versionType": "original_commit_for_fix"
            }
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        }
      ],
      "cpeApplicability": [
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                  "vulnerable": true
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\ntls: wait for pending async decryptions if tls_strp_msg_hold fails\n\nAsync decryption calls tls_strp_msg_hold to create a clone of the\ninput skb to hold references to the memory it uses. If we fail to\nallocate that clone, proceeding with async decryption can lead to\nvarious issues (UAF on the skb, writing into userspace memory after\nthe recv() call has returned).\n\nIn this case, wait for all pending decryption requests."
        }
      ],
      "metrics": [
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          "cvssV3_1": {
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            "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"
          },
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              "lang": "en",
              "value": "AV:N - The bug is in the kTLS software receive path (net/tls/tls_sw.c) processing TLS records supplied by the remote peer, with the record stream, sizes and record types fully controlled by that peer. Per kernel scoring guidance, kTLS bugs triggered by remote TLS peer data are Network.\nAC:L - Once the skb_clone()/alloc_skb() allocation fails, the outcome is deterministic, and a remote peer can drive the memory pressure that induces it by opening many connections and queueing large record backlogs (trivially so under memcg-constrained containers). The remaining conditions \u2014 TLS 1.2 plus an async-capable AEAD \u2014 are the default on affected stable kernels since x86 AES-NI GCM registers through the SIMD wrapper with CRYPTO_ALG_ASYNC.\nPR:N - The attacker is the remote TLS peer of an already-established kTLS connection and needs no privileges or account on the target system. The vulnerable code runs as part of normal server-side record processing.\nUI:N - No victim action beyond the server\u0027s ordinary recv()/recvmsg() loop, which runs automatically as part of serving the connection. No configuration change, file open, or mount is required.\nS:U - The corruption is confined to kernel memory and the receiving process\u0027s own address space within the same security authority. No VM, IOMMU, or sandbox boundary is crossed.\nC:H - The live strparser anchor skb is queued on async_hold and later freed by __skb_queue_purge() while strp-\u003eanchor still references it, giving a use-after-free on an skbuff that an attacker can reclaim with sprayed network data; the in-flight AEAD also reads input skb memory whose references were dropped. Per guidance, use-after-free is High.\nI:H - The UAF/double-free on the anchor skb yields a heap write primitive after slab reclaim, and the crypto engine additionally writes attacker-chosen plaintext into the pinned user pages after recv() has already returned, corrupting whatever the application has since placed in that buffer. Per guidance, use-after-free is High.\nA:H - The freed anchor skb remains reachable from softirq context via tls_strp_data_ready and is freed a second time by tls_strp_anchor_free() on close, causing oops/panic or slab corruption. Any use-after-free or double-free is High availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:08:21.202Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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        },
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        },
        {
          "url": "https://git.kernel.org/stable/c/4fc109d0ab196bd943b7451276690fb6bb48c2e0"
        },
        {
          "url": "https://git.kernel.org/stable/c/b8a6ff84abbcbbc445463de58704686011edc8e1"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40176",
    "datePublished": "2025-11-12T10:53:50.443Z",
    "dateReserved": "2025-04-16T07:20:57.177Z",
    "dateUpdated": "2026-08-05T12:08:21.202Z",
    "state": "PUBLISHED"
  },
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  "dataVersion": "5.2",
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      "date": "2026-08-05",
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    },
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-30T08:47:38+00:00",
      "cve": "CVE-2025-40176",
      "id": "CVE-2025-40176",
      "initial_release_date": "2025-11-12T00:00:00+00:00",
      "product_status:fixed": "1704",
      "product_status:known_not_affected": "112",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: tls: wait for pending async decryptions if tls_strp_msg_hold fails",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40176.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-07-31T01:03:02Z",
      "cve": "CVE-2025-40176",
      "id": "CVE-2025-40176",
      "initial_release_date": "2025-11-14T00:24:17Z",
      "product_status:first_fixed": "2",
      "product_status:known_affected": "394",
      "product_status:known_not_affected": "266",
      "product_status:recommended": "583",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-40176",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-40176.json",
      "version": "44"
    }
  }
}



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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.