CVE-2026-99056 (GCVE-0-2026-99056)

Vulnerability from cvelistv5 – Published: 2026-10-23 12:22 – Updated: 2026-10-24 14:10
VLAI
Title
strparser: make sure __strp_recv isn't running before tearing down the parser
Summary
In the Linux kernel, the following vulnerability has been resolved: strparser: make sure __strp_recv isn't running before tearing down the parser The comment above strp_done() claims that if strp is stopped, strp_recv will no longer be called. That's only true if the caller has a mechanism (eg locking) to guarantee that strp_recv() calls that started before strp_stop() have completed by the time we call strp_done(). This adds a dummy lock_sock/release_sock pair to guarantee that any in-flight strp_recv() (which runs under either bh_lock_sock or lock_sock, depending if it's called from ->sk_data_ready or strp_work) has completed. Only espintcp can be affected by this race condition, but this patch makes sure no future user of strp can have the bug. This could crash on strp->sk ("general mode" of strp), but this mode has been here for 9 years and has never been used. It'll be gone soon, no point worrying about it. Switch the stopped/paused/etc bits to u8's to avoid races between strp_stop() and strp_pause/unpause(). A reproducer has been published and turns the possible UAF into an exploit [1].
Severity
7.8 (High)
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Assigner
Linux CNA under the mitre root
CNA scorecard D 53/100 over 7067 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Linux Linux Affected: e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 , < a18dd388045dc7263d99a07db9de4e0f149ca8f1 (git)
Affected: e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 , < 9f3e9fe1b155e9b4572054d8d140586bc3512ecf (git)
Affected: e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 , < d2b5f637b9b67a79a50d42614d10653c13b4e449 (git)
Affected: e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 , < eaa3a29004c063d7e9d5ea55636f693f67e6db0f (git)
Affected: e27cca96cd68fa2c6814c90f9a1cfd36bb68c593 , < 0984ebc631792acf8fff105112ee74a6b8f1efcc (git)
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Linux Linux Affected: 5.6
Unaffected: 0 , < 5.6 (semver)
Unaffected: 6.6.160 , ≤ 6.6.* (semver)
Unaffected: 6.12.113 , ≤ 6.12.* (semver)
Unaffected: 6.18.57 , ≤ 6.18.* (semver)
Unaffected: 7.2.11 , ≤ 7.2.* (semver)
Unaffected: 7.3 , ≤ * (original_commit_for_fix)
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          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nstrparser: make sure __strp_recv isn\u0027t running before tearing down the parser\n\nThe comment above strp_done() claims that if strp is stopped,\nstrp_recv will no longer be called. That\u0027s only true if the caller has\na mechanism (eg locking) to guarantee that strp_recv() calls that\nstarted before strp_stop() have completed by the time we call\nstrp_done().\n\nThis adds a dummy lock_sock/release_sock pair to guarantee that any\nin-flight strp_recv() (which runs under either bh_lock_sock or\nlock_sock, depending if it\u0027s called from -\u003esk_data_ready or strp_work)\nhas completed.\n\nOnly espintcp can be affected by this race condition, but this patch\nmakes sure no future user of strp can have the bug.\n\nThis could crash on strp-\u003esk (\"general mode\" of strp), but this mode\nhas been here for 9 years and has never been used. It\u0027ll be gone soon,\nno point worrying about it.\n\nSwitch the stopped/paused/etc bits to u8\u0027s to avoid races between\nstrp_stop() and strp_pause/unpause().\n\nA reproducer has been published and turns the possible UAF into an\nexploit [1]."
        }
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            "version": "3.1"
          },
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              "value": "AV:L - An unprivileged local process can attach \"espintcp\" with setsockopt(TCP_ULP), then use a loopback peer to drive espintcp_data_ready()-\u003estrp_data_ready()-\u003e__strp_recv() while close() reaches espintcp_close()-\u003estrp_done(); a network peer alone cannot initiate the required local teardown.\nAC:L - The same process controls both race sides: it sets a finite SO_RCVTIMEO, sends complete keepalives plus a partial header that makes espintcp_parse() return 0 and strp_start_timer() rearm after strp_done() cancels, and concurrently closes the target socket. The race is repeatable and publicly exploited.\nPR:L - __sys_setsockopt()-\u003etcp_setsockopt()-\u003etcp_set_ulp()-\u003eespintcp_init_sk() contains no capability or authentication check for an already registered \"espintcp\" ULP. An ordinary local user can create the TCP pair, set the timeout, attach the ULP, and close it.\nUI:N - The attacking process performs the socket creation, TCP_ULP attachment, traffic generation, close, and heap reclaim itself; no action by another user is required.\nS:U - The reclaimed espintcp_ctx and its msg_timer_work execute within the host kernel reached by the attacking local process; this is a conventional local kernel privilege escalation and crosses no VM, IOMMU, or separate security authority.\nC:H - The freed espintcp_ctx can be reclaimed with a controlled user_key_payload, including msg_timer_work.timer.function and callback operands. The resulting kernel callback control and root execution permit access to arbitrary protected memory.\nI:H - The controlled timer.function and RDI-relative operands let the demonstrated iocg_flush_stat_upward gadget perform a chosen delta write to modprobe_path, producing root code execution.\nA:H - If the freed msg_timer_work is not coherently reclaimed, timer expiry consumes stale work_struct fields or calls an invalid timer.function, causing a kernel fault or panic; the published exploit also documents a crash-only variant."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-24T14:10:15.756Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
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    "cveId": "CVE-2026-99056",
    "datePublished": "2026-10-23T12:22:42.234Z",
    "dateReserved": "2026-09-25T10:25:14.388Z",
    "dateUpdated": "2026-10-24T14:10:15.756Z",
    "state": "PUBLISHED"
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      "date": "2026-10-26",
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      "cve": "CVE-2026-99056",
      "id": "msrc_CVE-2026-99056",
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      "product_status:under_investigation": "2",
      "source": "Microsoft CSAF VEX",
      "status": "final",
      "title": "strparser: make sure __strp_recv isn\u0027t running before tearing down the parser",
      "url": "https://msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-99056.json",
      "version": "2"
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            "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nstrparser: make sure __strp_recv isn\u0027t running before tearing down the parser\n\nThe comment above strp_done() claims that if strp is stopped,\nstrp_recv will no longer be called. That\u0027s only true if the caller has\na mechanism (eg locking) to guarantee that strp_recv() calls that\nstarted before strp_stop() have completed by the time we call\nstrp_done().\n\nThis adds a dummy lock_sock/release_sock pair to guarantee that any\nin-flight strp_recv() (which runs under either bh_lock_sock or\nlock_sock, depending if it\u0027s called from -\u003esk_data_ready or strp_work)\nhas completed.\n\nOnly espintcp can be affected by this race condition, but this patch\nmakes sure no future user of strp can have the bug.\n\nThis could crash on strp-\u003esk (\"general mode\" of strp), but this mode\nhas been here for 9 years and has never been used. It\u0027ll be gone soon,\nno point worrying about it.\n\nSwitch the stopped/paused/etc bits to u8\u0027s to avoid races between\nstrp_stop() and strp_pause/unpause().\n\nA reproducer has been published and turns the possible UAF into an\nexploit [1]."
          }
        ],
        "id": "CVE-2026-99056",
        "lastModified": "2026-10-24T14:16:54.200",
        "metrics": {
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      "current_release_date": "2026-10-27T03:13:53+00:00",
      "cve": "CVE-2026-99056",
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      "initial_release_date": "2026-10-23T00:00:00+00:00",
      "product_status:known_affected": "236",
      "product_status:known_not_affected": "42",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "kernel: strparser: make sure __strp_recv isn\u0027t running before tearing down the parser",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-99056.json",
      "version": "3"
    }
  }
}



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