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CVE-2025-40204 (GCVE-0-2025-40204)

Vulnerability from cvelistv5 – Published: 2025-11-12 21:56 – Updated: 2026-08-05 12:08
VLAI
Title
sctp: Fix MAC comparison to be constant-time
Summary
In the Linux kernel, the following vulnerability has been resolved: sctp: Fix MAC comparison to be constant-time To prevent timing attacks, MACs need to be compared in constant time. Use the appropriate helper function for this.
Severity
8.1 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Assigner
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < b93fa8dc521d00d2d44bf034fb90e0d79b036617 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 0e8b8c326c2a6de4d837b1bb034ea704f4690d77 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 1cd60e0d0fb8f0e62ec4499138afce6342dc9d4c (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 9c05d44ec24126fc283835b68f82dba3ae985209 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < ed3044b9c810c5c24eb2830053fbfe5fd134c5d4 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 8019b3699289fce3f10b63f98601db97b8d105b0 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < 0b32ff285ff6f6f1ac1d9495787ccce8837d6405 (git)
Affected: 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 , < dd91c79e4f58fbe2898dac84858033700e0e99fb (git)
guessed Create a notification for this product.
Linux Linux Affected: 2.6.12
Unaffected: 0 , < 2.6.12 (semver)
Unaffected: 5.4.301 , ≤ 5.4.* (semver)
Unaffected: 5.10.246 , ≤ 5.10.* (semver)
Unaffected: 5.15.195 , ≤ 5.15.* (semver)
Unaffected: 6.1.157 , ≤ 6.1.* (semver)
Unaffected: 6.6.113 , ≤ 6.6.* (semver)
Unaffected: 6.12.54 , ≤ 6.12.* (semver)
Unaffected: 6.17.4 , ≤ 6.17.* (semver)
Unaffected: 6.18 , ≤ * (original_commit_for_fix)
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{
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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\nsctp: Fix MAC comparison to be constant-time\n\nTo prevent timing attacks, MACs need to be compared in constant time.\nUse the appropriate helper function for this."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 8.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - Both vulnerable comparisons process data from remote SCTP peers \u2014 COOKIE ECHO chunks in `sctp_sf_do_5_1D_ce()`/`sctp_unpack_cookie()` and AUTH chunks in `sctp_sf_authenticate()` \u2014 delivered over IPv4/IPv6 from any routable host. No local access or network adjacency is required.\nAC:H - Exploitation requires statistically extracting nanosecond-scale timing deltas from the early-exit `memcmp` across network jitter and target CPU load, and on 64-bit architectures with `HAVE_EFFICIENT_UNALIGNED_ACCESS` the loop leaks only 8-byte-granular prefixes \u2014 conditions the attacker cannot influence. The bad-signature path is a silent `sctp_sf_pdiscard()`, so no direct request/response oracle exists.\nPR:N - The COOKIE ECHO path is reached pre-authentication on any listening SCTP socket, with the attacker supplying both the cookie contents and the matching verification tag, so no credentials or prior association state are needed. Cookie HMAC signing is enabled by default via `CONFIG_SCTP_DEFAULT_COOKIE_HMAC_MD5`.\nUI:N - The vulnerable comparisons execute automatically in the SCTP receive path for every COOKIE ECHO or AUTH chunk that reaches a listening endpoint or established association. No action by any local user or administrator is involved.\nS:U - The forged-MAC consequences \u2014 spoofed association establishment, out-of-bounds reads, and softirq hangs \u2014 all occur inside the kernel of the targeted host. No hypervisor, IOMMU, or sandbox boundary is crossed.\nC:H - A forged cookie MAC yields a fully attacker-controlled `struct sctp_cookie` whose unvalidated `raw_addr_list_len` drives an unbounded walk in `sctp_raw_to_bind_addrs()`, reading far past the skb. A forged SCTP-AUTH HMAC additionally allows ASCONF Add-IP injection to redirect an established association\u0027s data stream to the attacker.\nI:H - Recovering the MAC constitutes a complete bypass of SCTP\u0027s state-cookie and SCTP-AUTH authentication, letting an off-path attacker forge cookies to establish spoofed associations and inject arbitrary authenticated chunks into existing ones. The attacker-controlled cookie is copied wholesale into the new association via `memcpy(\u0026retval-\u003ec, bear_cookie, ...)` and fed to `sctp_process_init()`.\nA:H - With the cookie MAC forged, `sctp_raw_to_bind_addrs()` at this commit has no bounds checks \u2014 a zero-length address parameter makes `addrs_len -= len` never progress, producing an infinite loop in softirq context, while an oversized length causes an OOB read that can oops the kernel. Forged AUTH chunks also permit tearing down established associations."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:08:33.114Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
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          "url": "https://git.kernel.org/stable/c/b93fa8dc521d00d2d44bf034fb90e0d79b036617"
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          "url": "https://git.kernel.org/stable/c/0e8b8c326c2a6de4d837b1bb034ea704f4690d77"
        },
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        {
          "url": "https://git.kernel.org/stable/c/dd91c79e4f58fbe2898dac84858033700e0e99fb"
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      ],
      "title": "sctp: Fix MAC comparison to be constant-time",
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    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2025-40204",
    "datePublished": "2025-11-12T21:56:35.110Z",
    "dateReserved": "2025-04-16T07:20:57.179Z",
    "dateUpdated": "2026-08-05T12:08:33.114Z",
    "state": "PUBLISHED"
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  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
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      "date": "2026-09-15",
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    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-07-30T08:47:44+00:00",
      "cve": "CVE-2025-40204",
      "id": "CVE-2025-40204",
      "initial_release_date": "2025-11-12T00:00:00+00:00",
      "product_status:known_affected": "274",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: sctp: Fix MAC comparison to be constant-time",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-40204.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "important",
      "current_release_date": "2026-09-11T01:54:56Z",
      "cve": "CVE-2025-40204",
      "id": "CVE-2025-40204",
      "initial_release_date": "2025-11-14T00:23:44Z",
      "product_status:first_fixed": "2",
      "product_status:known_affected": "499",
      "product_status:known_not_affected": "6",
      "product_status:recommended": "884",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-40204",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-40204.json",
      "version": "66"
    }
  }
}



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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.