Vulnerability-Lookup

FKIE_CVE-2026-64560

Vulnerability from fkie_nvd - Published: 2026-07-29 17:16 - Updated: 2026-07-30 12:19

Severity

7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Summary

In the Linux kernel, the following vulnerability has been resolved: posix-cpu-timers: Prevent UAF caused by non-leader exec() race Wongi and Jungwoo decoded and reported a non-leader exec() related race which can result in an UAF: sys_timer_delete() exec() posix_cpu_timer_del() // Observes old leader p = pid_task(pid, pid_type); de_thread() switch_leader(); release_task(old_leader) __exit_signal(old_leader) sighand = lock(old_leader, sighand); posix_cpu_timers*_exit(); sighand = lock_task_sighand(p) unhash_task(old_leader); sh = lock(p, sighand) old_leader->sighand = NULL; unlock(sighand); (p->sighand == NULL) unlock(sh) return NULL; // Returns without action if(!sighand) return 0; free_posix_timer(); This is "harmless" unless the deleted timer was armed and enqueued in p->signal because on exec() a TGID targeted timer is inherited. As sys_timer_delete() freed the underlying posix timer object run_posix_cpu_timers() or any timerqueue related add/delete operations on other timers will access the freed object's timerqueue node, which results in an UAF. There is a similar problem vs. posix_cpu_timer_set(). For regular posix timers it just transiently returns -ESRCH to user space, but for the use case in do_cpu_nanosleep() it's the same UAF just that the k_itimer is allocated on the stack. Also posix_cpu_timer_rearm() fails to rearm the timer, which means it stops to expire. While debating solutions Frederic pointed out another problem: posix_cpu_timer_del(tmr) __exit_signal(p) posix_cpu_timers*_exit(p); unhash_task(p); p->sighand = NULL; sh = lock_task_sighand(p) sighand = p->sighand; if (!sighand) return NULL; lock(sighand); if (!sh) WARN_ON_ONCE(timer_queued(tmr)); On weakly ordered architectures it is not guaranteed that posix_cpu_timer_del() will observe the stores in posix_cpu_timers*_exit() when p->sighand is observed as NULL, which means the WARN() can be a false positive. Solve these issues by: 1) Changing the store in __exit_signal() to smp_store_release(). 2) Adding a smp_acquire__after_ctrl_dep() into the !sighand path of lock_task_sighand(). 3) Creating a helper function for looking up the task and locking sighand which does not return when sighand == NULL. Instead it retries the task lookup and only if that fails it gives up. 4) Using that helper in the three affected functions. #1/#2 ensures that the reader side which observes sighand == NULL also observes all preceeding stores, i.e. the stores in posix_cpu_timers*_exit() and the ones in unhash_task(). #3 ensures that the above described non-leader exec() situation is handled gracefully. When the task lookup returns the old leader, but sighand == NULL then it retries. In the non-leader exec() case the subsequent task lookup will observe the new leader due to #1/#2. In normal exit() scenarios the subsequent lookup fails. When the task lookup fails, the function also checks whether the timer is still enqueued and issues a warning if that's the case. Unfortunately there is nothing which can be done about it, but as the task is already not longer visible the timer should not be accessed anymore. This check also requires memory ordering, which is not provided when the first lookup fails. To achieve that the check is preceeded by a smp_rmb() which pairs with the smp_wmb() in write_seqlock() in __exit_signal(). That ensures that the stores in posix_cpu_timers*_exit() are visible. The history of the non-leader exec() issue goes back to the early days of posix CPU timers, which stored a pointer to the group leader task in the timer. That obviously fails when a non-leader exec() switches the leader. commit e0a70217107e ("posix-cpu-timers: workaround to suppress the problems with mt exec") added a temporary workaround for that in 2010 which surv ---truncated---

References

	URL	Tags
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/12a891c773aeb5823d63dbd0cb2ab931d6c21c9b
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/67aa823e3e8c229c6d374df79c804f6721cb83b6
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/6a7ecc25abe6f0fecc6e62a05096987200edbd02
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/920f893f735e92ba3a1cd9256899a186b161928d
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/ad1cafa1bdaa71da85d71cac053838bbe97852b6
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/cc35ddbc497311e0b6b9a6a6a4f4d1217d6ab1aa
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/d8bcb28abad857f1415da7656f19b2ada90af04f
	416baaa9-dc9f-4396-8d5f-8c081fb06d67	https://git.kernel.org/stable/c/e74443f5db0037c556ef436fa64b88bf4ea08f83

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/exit.c",
            "kernel/signal.c",
            "kernel/time/posix-cpu-timers.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "67aa823e3e8c229c6d374df79c804f6721cb83b6",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "d8bcb28abad857f1415da7656f19b2ada90af04f",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "cc35ddbc497311e0b6b9a6a6a4f4d1217d6ab1aa",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "12a891c773aeb5823d63dbd0cb2ab931d6c21c9b",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "e74443f5db0037c556ef436fa64b88bf4ea08f83",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "6a7ecc25abe6f0fecc6e62a05096987200edbd02",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "ad1cafa1bdaa71da85d71cac053838bbe97852b6",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "920f893f735e92ba3a1cd9256899a186b161928d",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/exit.c",
            "kernel/signal.c",
            "kernel/time/posix-cpu-timers.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.7"
            },
            {
              "lessThan": "5.7",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.262",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.213",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.180",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.147",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.100",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.41",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nposix-cpu-timers: Prevent UAF caused by non-leader exec() race\n\nWongi and Jungwoo decoded and reported a non-leader exec() related race\nwhich can result in an UAF:\n\n sys_timer_delete()\t\t\texec()\n   posix_cpu_timer_del()\n   // Observes old leader\n   p = pid_task(pid, pid_type);\t\tde_thread()\n   \t\t\t\t\t  switch_leader();\n\t\t\t\t\t  release_task(old_leader)\n\t\t\t\t\t    __exit_signal(old_leader)\n\t\t\t\t\t      sighand = lock(old_leader, sighand);\n\t\t\t\t\t      posix_cpu_timers*_exit();\n   sighand = lock_task_sighand(p)\t      unhash_task(old_leader);\n     sh = lock(p, sighand)\t    \t      old_leader-\u003esighand = NULL;\n\t\t\t\t\t      unlock(sighand);\n     (p-\u003esighand == NULL)\n\tunlock(sh)\n\treturn NULL;\n\n   // Returns without action\n   if(!sighand)\n      return 0;\n   free_posix_timer();\n\nThis is \"harmless\" unless the deleted timer was armed and enqueued in\np-\u003esignal because on exec() a TGID targeted timer is inherited.\n\nAs sys_timer_delete() freed the underlying posix timer object\nrun_posix_cpu_timers() or any timerqueue related add/delete operations on\nother timers will access the freed object\u0027s timerqueue node, which results\nin an UAF.\n\nThere is a similar problem vs. posix_cpu_timer_set(). For regular posix\ntimers it just transiently returns -ESRCH to user space, but for the use\ncase in do_cpu_nanosleep() it\u0027s the same UAF just that the k_itimer is\nallocated on the stack.\n\nAlso posix_cpu_timer_rearm() fails to rearm the timer, which means it stops\nto expire.\n\nWhile debating solutions Frederic pointed out another problem:\n\n   posix_cpu_timer_del(tmr)\n\t\t\t\t\t__exit_signal(p)\n\t\t\t\t\t  posix_cpu_timers*_exit(p);\n\t\t\t\t\t  unhash_task(p);\n\t\t\t\t\t  p-\u003esighand = NULL;\n     sh = lock_task_sighand(p)\n        sighand = p-\u003esighand;\n\tif (!sighand)\n\t    return NULL;\n\tlock(sighand);\n\n     if (!sh)\n\tWARN_ON_ONCE(timer_queued(tmr));\n\nOn weakly ordered architectures it is not guaranteed that\nposix_cpu_timer_del() will observe the stores in posix_cpu_timers*_exit()\nwhen p-\u003esighand is observed as NULL, which means the WARN() can be a false\npositive.\n\nSolve these issues by:\n\n  1) Changing the store in __exit_signal() to smp_store_release().\n\n  2) Adding a smp_acquire__after_ctrl_dep() into the !sighand path\n     of lock_task_sighand().\n\n  3) Creating a helper function for looking up the task and locking sighand\n     which does not return when sighand == NULL. Instead it retries the\n     task lookup and only if that fails it gives up.\n\n  4) Using that helper in the three affected functions.\n\n#1/#2 ensures that the reader side which observes sighand == NULL also\nobserves all preceeding stores, i.e. the stores in posix_cpu_timers*_exit()\nand the ones in unhash_task().\n\n#3 ensures that the above described non-leader exec() situation is handled\ngracefully. When the task lookup returns the old leader, but sighand ==\nNULL then it retries. In the non-leader exec() case the subsequent task\nlookup will observe the new leader due to #1/#2. In normal exit() scenarios\nthe subsequent lookup fails.\n\nWhen the task lookup fails, the function also checks whether the timer is\nstill enqueued and issues a warning if that\u0027s the case. Unfortunately there\nis nothing which can be done about it, but as the task is already not\nlonger visible the timer should not be accessed anymore. This check also\nrequires memory ordering, which is not provided when the first lookup\nfails. To achieve that the check is preceeded by a smp_rmb() which pairs\nwith the smp_wmb() in write_seqlock() in __exit_signal(). That ensures that\nthe stores in posix_cpu_timers*_exit() are visible.\n\nThe history of the non-leader exec() issue goes back to the early days of\nposix CPU timers, which stored a pointer to the group leader task in the\ntimer. That obviously fails when a non-leader exec() switches the leader.\ncommit e0a70217107e (\"posix-cpu-timers: workaround to suppress the problems\nwith mt exec\") added a temporary workaround for that in 2010 which surv\n---truncated---"
    }
  ],
  "id": "CVE-2026-64560",
  "lastModified": "2026-07-30T12:19:03.630",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-07-29T17:16:53.637",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/12a891c773aeb5823d63dbd0cb2ab931d6c21c9b"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/67aa823e3e8c229c6d374df79c804f6721cb83b6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/6a7ecc25abe6f0fecc6e62a05096987200edbd02"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/920f893f735e92ba3a1cd9256899a186b161928d"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/ad1cafa1bdaa71da85d71cac053838bbe97852b6"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/cc35ddbc497311e0b6b9a6a6a4f4d1217d6ab1aa"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/d8bcb28abad857f1415da7656f19b2ada90af04f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e74443f5db0037c556ef436fa64b88bf4ea08f83"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}

CVE-2026-64560 (GCVE-0-2026-64560)

Vulnerability from cvelistv5 – Published: 2026-07-29 16:47 – Updated: 2026-08-05 12:43

Title

posix-cpu-timers: Prevent UAF caused by non-leader exec() race

Summary

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

References

8 references

URL	Tags
https://git.kernel.org/stable/c/67aa823e3e8c229c6…
https://git.kernel.org/stable/c/d8bcb28abad857f14…
https://git.kernel.org/stable/c/cc35ddbc497311e0b…
https://git.kernel.org/stable/c/12a891c773aeb5823…
https://git.kernel.org/stable/c/e74443f5db0037c55…
https://git.kernel.org/stable/c/6a7ecc25abe6f0fec…
https://git.kernel.org/stable/c/ad1cafa1bdaa71da8…
https://git.kernel.org/stable/c/920f893f735e92ba3…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < 67aa823e3e8c229c6d374df79c804f6721cb83b6 (git) Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < d8bcb28abad857f1415da7656f19b2ada90af04f (git) Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < cc35ddbc497311e0b6b9a6a6a4f4d1217d6ab1aa (git) Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < 12a891c773aeb5823d63dbd0cb2ab931d6c21c9b (git) Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < e74443f5db0037c556ef436fa64b88bf4ea08f83 (git) Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < 6a7ecc25abe6f0fecc6e62a05096987200edbd02 (git) Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < ad1cafa1bdaa71da85d71cac053838bbe97852b6 (git) Affected: 55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59 , < 920f893f735e92ba3a1cd9256899a186b161928d (git)
Linux	Linux	Affected: 5.7 Unaffected: 0 , < 5.7 (semver) Unaffected: 5.10.262 , ≤ 5.10.* (semver) Unaffected: 5.15.213 , ≤ 5.15.* (semver) Unaffected: 6.1.180 , ≤ 6.1.* (semver) Unaffected: 6.6.147 , ≤ 6.6.* (semver) Unaffected: 6.12.100 , ≤ 6.12.* (semver) Unaffected: 6.18.41 , ≤ 6.18.* (semver) Unaffected: 7.1.5 , ≤ 7.1.* (semver) Unaffected: 7.2-rc3 , ≤ * (original_commit_for_fix)

Show details on NVD website

JSON

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{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "kernel/exit.c",
            "kernel/signal.c",
            "kernel/time/posix-cpu-timers.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "67aa823e3e8c229c6d374df79c804f6721cb83b6",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "d8bcb28abad857f1415da7656f19b2ada90af04f",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "cc35ddbc497311e0b6b9a6a6a4f4d1217d6ab1aa",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "12a891c773aeb5823d63dbd0cb2ab931d6c21c9b",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "e74443f5db0037c556ef436fa64b88bf4ea08f83",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "6a7ecc25abe6f0fecc6e62a05096987200edbd02",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "ad1cafa1bdaa71da85d71cac053838bbe97852b6",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            },
            {
              "lessThan": "920f893f735e92ba3a1cd9256899a186b161928d",
              "status": "affected",
              "version": "55e8c8eb2c7b6bf30e99423ccfe7ca032f498f59",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "kernel/exit.c",
            "kernel/signal.c",
            "kernel/time/posix-cpu-timers.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "5.7"
            },
            {
              "lessThan": "5.7",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.10.*",
              "status": "unaffected",
              "version": "5.10.262",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "5.15.*",
              "status": "unaffected",
              "version": "5.15.213",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.1.*",
              "status": "unaffected",
              "version": "6.1.180",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.147",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.100",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.41",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.1.*",
              "status": "unaffected",
              "version": "7.1.5",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.2-rc3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.10.262",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "5.15.213",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.1.180",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.6.147",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.12.100",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.41",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.1.5",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2-rc3",
                  "versionStartIncluding": "5.7",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nposix-cpu-timers: Prevent UAF caused by non-leader exec() race\n\nWongi and Jungwoo decoded and reported a non-leader exec() related race\nwhich can result in an UAF:\n\n sys_timer_delete()\t\t\texec()\n   posix_cpu_timer_del()\n   // Observes old leader\n   p = pid_task(pid, pid_type);\t\tde_thread()\n   \t\t\t\t\t  switch_leader();\n\t\t\t\t\t  release_task(old_leader)\n\t\t\t\t\t    __exit_signal(old_leader)\n\t\t\t\t\t      sighand = lock(old_leader, sighand);\n\t\t\t\t\t      posix_cpu_timers*_exit();\n   sighand = lock_task_sighand(p)\t      unhash_task(old_leader);\n     sh = lock(p, sighand)\t    \t      old_leader-\u003esighand = NULL;\n\t\t\t\t\t      unlock(sighand);\n     (p-\u003esighand == NULL)\n\tunlock(sh)\n\treturn NULL;\n\n   // Returns without action\n   if(!sighand)\n      return 0;\n   free_posix_timer();\n\nThis is \"harmless\" unless the deleted timer was armed and enqueued in\np-\u003esignal because on exec() a TGID targeted timer is inherited.\n\nAs sys_timer_delete() freed the underlying posix timer object\nrun_posix_cpu_timers() or any timerqueue related add/delete operations on\nother timers will access the freed object\u0027s timerqueue node, which results\nin an UAF.\n\nThere is a similar problem vs. posix_cpu_timer_set(). For regular posix\ntimers it just transiently returns -ESRCH to user space, but for the use\ncase in do_cpu_nanosleep() it\u0027s the same UAF just that the k_itimer is\nallocated on the stack.\n\nAlso posix_cpu_timer_rearm() fails to rearm the timer, which means it stops\nto expire.\n\nWhile debating solutions Frederic pointed out another problem:\n\n   posix_cpu_timer_del(tmr)\n\t\t\t\t\t__exit_signal(p)\n\t\t\t\t\t  posix_cpu_timers*_exit(p);\n\t\t\t\t\t  unhash_task(p);\n\t\t\t\t\t  p-\u003esighand = NULL;\n     sh = lock_task_sighand(p)\n        sighand = p-\u003esighand;\n\tif (!sighand)\n\t    return NULL;\n\tlock(sighand);\n\n     if (!sh)\n\tWARN_ON_ONCE(timer_queued(tmr));\n\nOn weakly ordered architectures it is not guaranteed that\nposix_cpu_timer_del() will observe the stores in posix_cpu_timers*_exit()\nwhen p-\u003esighand is observed as NULL, which means the WARN() can be a false\npositive.\n\nSolve these issues by:\n\n  1) Changing the store in __exit_signal() to smp_store_release().\n\n  2) Adding a smp_acquire__after_ctrl_dep() into the !sighand path\n     of lock_task_sighand().\n\n  3) Creating a helper function for looking up the task and locking sighand\n     which does not return when sighand == NULL. Instead it retries the\n     task lookup and only if that fails it gives up.\n\n  4) Using that helper in the three affected functions.\n\n#1/#2 ensures that the reader side which observes sighand == NULL also\nobserves all preceeding stores, i.e. the stores in posix_cpu_timers*_exit()\nand the ones in unhash_task().\n\n#3 ensures that the above described non-leader exec() situation is handled\ngracefully. When the task lookup returns the old leader, but sighand ==\nNULL then it retries. In the non-leader exec() case the subsequent task\nlookup will observe the new leader due to #1/#2. In normal exit() scenarios\nthe subsequent lookup fails.\n\nWhen the task lookup fails, the function also checks whether the timer is\nstill enqueued and issues a warning if that\u0027s the case. Unfortunately there\nis nothing which can be done about it, but as the task is already not\nlonger visible the timer should not be accessed anymore. This check also\nrequires memory ordering, which is not provided when the first lookup\nfails. To achieve that the check is preceeded by a smp_rmb() which pairs\nwith the smp_wmb() in write_seqlock() in __exit_signal(). That ensures that\nthe stores in posix_cpu_timers*_exit() are visible.\n\nThe history of the non-leader exec() issue goes back to the early days of\nposix CPU timers, which stored a pointer to the group leader task in the\ntimer. That obviously fails when a non-leader exec() switches the leader.\ncommit e0a70217107e (\"posix-cpu-timers: workaround to suppress the problems\nwith mt exec\") added a temporary workaround for that in 2010 which surv\n---truncated---"
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerability is reached purely through local syscalls (`timer_create`/`timer_settime`/`timer_delete`/`clock_nanosleep`) raced against `execve()` from a non-leader thread in the attacker\u0027s own process. No network or remote data path reaches posix-cpu-timers.\nAC:L - The attacker controls both sides of the race \u2014 one thread arms and deletes a process-wide CPU timer while a non-leader thread in the same process calls `execve()` \u2014 and can loop indefinitely with CPU pinning/thread spraying to widen the window between `pid_task()` and `lock_task_sighand()`. No condition depends on anything outside attacker control.\nPR:L - Any ordinary unprivileged local user can create and delete `CLOCK_PROCESS_CPUTIME_ID` timers; `pid_for_clock()` performs no capability check when the encoded PID is 0, and `CONFIG_POSIX_TIMERS` is `default y` on essentially all deployments.\nUI:N - The attacker performs every step \u2014 timer creation, arming, deletion, and the concurrent non-leader exec \u2014 entirely within its own multithreaded process. No victim action is involved.\nS:U - The corruption stays within the kernel\u0027s own security authority; it is a standard local kernel memory-corruption/privilege-escalation primitive with no VM, IOMMU, or hypervisor boundary crossed.\nC:H - The stale timerqueue node yields UAF reads of the freed `k_itimer` and causes `current` (a live `task_struct` pointer) plus rbtree pointers to be written into the freed/reallocated slot, and the freed object can be reclaimed by another attacker-created `k_itimer`, enabling kernel pointer disclosure and broad memory read.\nI:H - `collect_timerqueue()` writes into freed memory (`ctmr-\u003efiring`, `ctmr-\u003ehandling`, rbtree rebalancing, list insertion) and the `do_cpu_nanosleep()` variant does so into a live, attacker-groomed kernel stack frame, followed by `cpu_timer_fire()` dereferencing attacker-controlled `it_process`/`it_signal` \u2014 a control-flow-hijack-capable write primitive.\nA:H - Even without exploitation the dangling timerqueue node produces rbtree/list corruption and a kernel oops, and the pre-fix `WARN_ON_ONCE(timerqueue_node_queued(...))` is an immediate panic under `panic_on_warn`; the race can be triggered repeatedly by any local user."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-05T12:43:06.059Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/67aa823e3e8c229c6d374df79c804f6721cb83b6"
        },
        {
          "url": "https://git.kernel.org/stable/c/d8bcb28abad857f1415da7656f19b2ada90af04f"
        },
        {
          "url": "https://git.kernel.org/stable/c/cc35ddbc497311e0b6b9a6a6a4f4d1217d6ab1aa"
        },
        {
          "url": "https://git.kernel.org/stable/c/12a891c773aeb5823d63dbd0cb2ab931d6c21c9b"
        },
        {
          "url": "https://git.kernel.org/stable/c/e74443f5db0037c556ef436fa64b88bf4ea08f83"
        },
        {
          "url": "https://git.kernel.org/stable/c/6a7ecc25abe6f0fecc6e62a05096987200edbd02"
        },
        {
          "url": "https://git.kernel.org/stable/c/ad1cafa1bdaa71da85d71cac053838bbe97852b6"
        },
        {
          "url": "https://git.kernel.org/stable/c/920f893f735e92ba3a1cd9256899a186b161928d"
        }
      ],
      "title": "posix-cpu-timers: Prevent UAF caused by non-leader exec() race",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64560",
    "datePublished": "2026-07-29T16:47:17.602Z",
    "dateReserved": "2026-07-19T15:36:31.796Z",
    "dateUpdated": "2026-08-05T12:43:06.059Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

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FKIE_CVE-2026-64560

CVE-2026-64560 (GCVE-0-2026-64560)

Tags

Sightings

Nomenclature