Vulnerability-Lookup

BDU:2025-04406 (CVE-2025-21896)

Vulnerability from fstec – Published: 2025-04-14 – Updated: 2025-04-14 – View on bdu.fstec.ru Fixed

Title

Уязвимость компонента fuse функции __readahead_folio ядра операционной системы Linux, позволяющая нарушителю раскрыть защищаемую информацию

Summary

Уязвимость компонента fuse функции __readahead_folio ядра операционной системы Linux связана с недостаточной защитой служебных данных. Эксплуатация уязвимости может позволить нарушителю, действующему удаленно, раскрыть защищаемую информацию

Severity

2.7 (Low) CVSS 2.0


                      
                        AV:A/AC:L/Au:S/C:P/I:N/A:N

3.5 (Low) CVSS 3.0


                      
                        CVSS:3.0/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

Class

Code vulnerability

Status

Confirmed by the vendor

Exploitation

Information gathering

Incidents

Being clarified

Remediation

Software update

CWE

CWE-200 - Раскрытие информации

Aliases

CVE-2025-21896

References

5 references

URL
https://git.kernel.org/stable/c/0c67c37e1710b2a8f61c8a02db95a51fe577e2c1
https://git.kernel.org/stable/c/60db11f1b7fba4a66b117ea998d965818784a98d
https://lore.kernel.org/linux-cve-announce/2025040132-CVE-2025-21896-395c@gregkh/
https://security-tracker.debian.org/tracker/CVE-2025-21896
https://vuldb.com/ru/?id.302619

Impacted products

2 products from 1 vendor

Vendors

Сообщество свободного программного обеспечения

Products

Debian GNU/Linux, Linux

Versions

11 (Debian GNU/Linux), 12 (Debian GNU/Linux), от 6.13 до 6.13.6 (Linux), от 6.13 до 6.14 (Linux)

Product types

Operating system

Platforms

Сообщество свободного программного обеспечения Debian GNU/Linux 11, Сообщество свободного программного обеспечения Debian GNU/Linux 12, Сообщество свободного программного обеспечения Linux от 6.13 до 6.13.6, Сообщество свободного программного обеспечения Linux от 6.13 до 6.14

Mitigations

В условиях отсутствия обновлений безопасности от производителя рекомендуется придерживаться "Рекомендаций по безопасной настройке операционных систем LINUX", изложенных в методическом документе ФСТЭК России, утверждённом 25 декабря 2022 года. Использование рекомендаций: Для Linux: https://git.kernel.org/stable/c/0c67c37e1710b2a8f61c8a02db95a51fe577e2c1 https://git.kernel.org/stable/c/60db11f1b7fba4a66b117ea998d965818784a98d https://lore.kernel.org/linux-cve-announce/2025040132-CVE-2025-21896-395c@gregkh/ Для Debian GNU/Linux: https://security-tracker.debian.org/tracker/CVE-2025-21896

JSON

To clipboard

{
  "CVSS 2.0": "AV:A/AC:L/Au:S/C:P/I:N/A:N",
  "CVSS 3.0": "AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
  "CVSS 4.0": null,
  "remediation_\u0418\u0434\u0435\u043d\u0442\u0438\u0444\u0438\u043a\u0430\u0442\u043e\u0440": null,
  "remediation_\u041d\u0430\u0438\u043c\u0435\u043d\u043e\u0432\u0430\u043d\u0438\u0435": null,
  "\u0412\u0435\u043d\u0434\u043e\u0440 \u041f\u041e": "\u0421\u043e\u043e\u0431\u0449\u0435\u0441\u0442\u0432\u043e \u0441\u0432\u043e\u0431\u043e\u0434\u043d\u043e\u0433\u043e \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u043d\u043e\u0433\u043e \u043e\u0431\u0435\u0441\u043f\u0435\u0447\u0435\u043d\u0438\u044f",
  "\u0412\u0435\u0440\u0441\u0438\u044f \u041f\u041e": "11 (Debian GNU/Linux), 12 (Debian GNU/Linux), \u043e\u0442 6.13 \u0434\u043e 6.13.6 (Linux), \u043e\u0442 6.13 \u0434\u043e 6.14 (Linux)",
  "\u0412\u043e\u0437\u043c\u043e\u0436\u043d\u044b\u0435 \u043c\u0435\u0440\u044b \u043f\u043e \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u044e": "\u0412 \u0443\u0441\u043b\u043e\u0432\u0438\u044f\u0445 \u043e\u0442\u0441\u0443\u0442\u0441\u0442\u0432\u0438\u044f \u043e\u0431\u043d\u043e\u0432\u043b\u0435\u043d\u0438\u0439 \u0431\u0435\u0437\u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438 \u043e\u0442 \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0438\u0442\u0435\u043b\u044f \u0440\u0435\u043a\u043e\u043c\u0435\u043d\u0434\u0443\u0435\u0442\u0441\u044f \u043f\u0440\u0438\u0434\u0435\u0440\u0436\u0438\u0432\u0430\u0442\u044c\u0441\u044f \"\u0420\u0435\u043a\u043e\u043c\u0435\u043d\u0434\u0430\u0446\u0438\u0439 \u043f\u043e \u0431\u0435\u0437\u043e\u043f\u0430\u0441\u043d\u043e\u0439 \u043d\u0430\u0441\u0442\u0440\u043e\u0439\u043a\u0435 \u043e\u043f\u0435\u0440\u0430\u0446\u0438\u043e\u043d\u043d\u044b\u0445 \u0441\u0438\u0441\u0442\u0435\u043c LINUX\", \u0438\u0437\u043b\u043e\u0436\u0435\u043d\u043d\u044b\u0445 \u0432 \u043c\u0435\u0442\u043e\u0434\u0438\u0447\u0435\u0441\u043a\u043e\u043c \u0434\u043e\u043a\u0443\u043c\u0435\u043d\u0442\u0435 \u0424\u0421\u0422\u042d\u041a \u0420\u043e\u0441\u0441\u0438\u0438, \u0443\u0442\u0432\u0435\u0440\u0436\u0434\u0451\u043d\u043d\u043e\u043c 25 \u0434\u0435\u043a\u0430\u0431\u0440\u044f 2022 \u0433\u043e\u0434\u0430.\n\n\u0418\u0441\u043f\u043e\u043b\u044c\u0437\u043e\u0432\u0430\u043d\u0438\u0435 \u0440\u0435\u043a\u043e\u043c\u0435\u043d\u0434\u0430\u0446\u0438\u0439:\n\u0414\u043b\u044f Linux:\nhttps://git.kernel.org/stable/c/0c67c37e1710b2a8f61c8a02db95a51fe577e2c1\t\nhttps://git.kernel.org/stable/c/60db11f1b7fba4a66b117ea998d965818784a98d\t\nhttps://lore.kernel.org/linux-cve-announce/2025040132-CVE-2025-21896-395c@gregkh/\n\n\u0414\u043b\u044f Debian GNU/Linux:\nhttps://security-tracker.debian.org/tracker/CVE-2025-21896",
  "\u0414\u0430\u0442\u0430 \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0438\u044f": "11.02.2025",
  "\u0414\u0430\u0442\u0430 \u043f\u043e\u0441\u043b\u0435\u0434\u043d\u0435\u0433\u043e \u043e\u0431\u043d\u043e\u0432\u043b\u0435\u043d\u0438\u044f": "14.04.2025",
  "\u0414\u0430\u0442\u0430 \u043f\u0443\u0431\u043b\u0438\u043a\u0430\u0446\u0438\u0438": "14.04.2025",
  "\u0418\u0434\u0435\u043d\u0442\u0438\u0444\u0438\u043a\u0430\u0442\u043e\u0440": "BDU:2025-04406",
  "\u0418\u0434\u0435\u043d\u0442\u0438\u0444\u0438\u043a\u0430\u0442\u043e\u0440\u044b \u0434\u0440\u0443\u0433\u0438\u0445 \u0441\u0438\u0441\u0442\u0435\u043c \u043e\u043f\u0438\u0441\u0430\u043d\u0438\u0439 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "CVE-2025-21896",
  "\u0418\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u044f \u043e\u0431 \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u0438": "\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0430",
  "\u041a\u043b\u0430\u0441\u0441 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u043a\u043e\u0434\u0430",
  "\u041d\u0430\u0437\u0432\u0430\u043d\u0438\u0435 \u041f\u041e": "Debian GNU/Linux, Linux",
  "\u041d\u0430\u0438\u043c\u0435\u043d\u043e\u0432\u0430\u043d\u0438\u0435 \u041e\u0421 \u0438 \u0442\u0438\u043f \u0430\u043f\u043f\u0430\u0440\u0430\u0442\u043d\u043e\u0439 \u043f\u043b\u0430\u0442\u0444\u043e\u0440\u043c\u044b": "\u0421\u043e\u043e\u0431\u0449\u0435\u0441\u0442\u0432\u043e \u0441\u0432\u043e\u0431\u043e\u0434\u043d\u043e\u0433\u043e \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u043d\u043e\u0433\u043e \u043e\u0431\u0435\u0441\u043f\u0435\u0447\u0435\u043d\u0438\u044f Debian GNU/Linux 11 , \u0421\u043e\u043e\u0431\u0449\u0435\u0441\u0442\u0432\u043e \u0441\u0432\u043e\u0431\u043e\u0434\u043d\u043e\u0433\u043e \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u043d\u043e\u0433\u043e \u043e\u0431\u0435\u0441\u043f\u0435\u0447\u0435\u043d\u0438\u044f Debian GNU/Linux 12 , \u0421\u043e\u043e\u0431\u0449\u0435\u0441\u0442\u0432\u043e \u0441\u0432\u043e\u0431\u043e\u0434\u043d\u043e\u0433\u043e \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u043d\u043e\u0433\u043e \u043e\u0431\u0435\u0441\u043f\u0435\u0447\u0435\u043d\u0438\u044f Linux \u043e\u0442 6.13 \u0434\u043e 6.13.6 , \u0421\u043e\u043e\u0431\u0449\u0435\u0441\u0442\u0432\u043e \u0441\u0432\u043e\u0431\u043e\u0434\u043d\u043e\u0433\u043e \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u043d\u043e\u0433\u043e \u043e\u0431\u0435\u0441\u043f\u0435\u0447\u0435\u043d\u0438\u044f Linux \u043e\u0442 6.13 \u0434\u043e 6.14 ",
  "\u041d\u0430\u0438\u043c\u0435\u043d\u043e\u0432\u0430\u043d\u0438\u0435 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u043a\u043e\u043c\u043f\u043e\u043d\u0435\u043d\u0442\u0430 fuse \u0444\u0443\u043d\u043a\u0446\u0438\u0438 __readahead_folio \u044f\u0434\u0440\u0430 \u043e\u043f\u0435\u0440\u0430\u0446\u0438\u043e\u043d\u043d\u043e\u0439 \u0441\u0438\u0441\u0442\u0435\u043c\u044b Linux, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u043d\u0430\u0440\u0443\u0448\u0438\u0442\u0435\u043b\u044e \u0440\u0430\u0441\u043a\u0440\u044b\u0442\u044c \u0437\u0430\u0449\u0438\u0449\u0430\u0435\u043c\u0443\u044e \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u044e",
  "\u041d\u0430\u043b\u0438\u0447\u0438\u0435 \u044d\u043a\u0441\u043f\u043b\u043e\u0439\u0442\u0430": "\u0414\u0430\u043d\u043d\u044b\u0435 \u0443\u0442\u043e\u0447\u043d\u044f\u044e\u0442\u0441\u044f",
  "\u041e\u043f\u0438\u0441\u0430\u043d\u0438\u0435 \u043e\u0448\u0438\u0431\u043a\u0438 CWE": "\u0420\u0430\u0441\u043a\u0440\u044b\u0442\u0438\u0435 \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u0438 (CWE-200)",
  "\u041e\u043f\u0438\u0441\u0430\u043d\u0438\u0435 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u0423\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u044c \u043a\u043e\u043c\u043f\u043e\u043d\u0435\u043d\u0442\u0430 fuse \u0444\u0443\u043d\u043a\u0446\u0438\u0438 __readahead_folio \u044f\u0434\u0440\u0430 \u043e\u043f\u0435\u0440\u0430\u0446\u0438\u043e\u043d\u043d\u043e\u0439 \u0441\u0438\u0441\u0442\u0435\u043c\u044b Linux \u0441\u0432\u044f\u0437\u0430\u043d\u0430 \u0441 \u043d\u0435\u0434\u043e\u0441\u0442\u0430\u0442\u043e\u0447\u043d\u043e\u0439 \u0437\u0430\u0449\u0438\u0442\u043e\u0439 \u0441\u043b\u0443\u0436\u0435\u0431\u043d\u044b\u0445 \u0434\u0430\u043d\u043d\u044b\u0445. \u042d\u043a\u0441\u043f\u043b\u0443\u0430\u0442\u0430\u0446\u0438\u044f \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438 \u043c\u043e\u0436\u0435\u0442 \u043f\u043e\u0437\u0432\u043e\u043b\u0438\u0442\u044c \u043d\u0430\u0440\u0443\u0448\u0438\u0442\u0435\u043b\u044e, \u0434\u0435\u0439\u0441\u0442\u0432\u0443\u044e\u0449\u0435\u043c\u0443 \u0443\u0434\u0430\u043b\u0435\u043d\u043d\u043e, \u0440\u0430\u0441\u043a\u0440\u044b\u0442\u044c \u0437\u0430\u0449\u0438\u0449\u0430\u0435\u043c\u0443\u044e \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u044e",
  "\u041f\u043e\u0441\u043b\u0435\u0434\u0441\u0442\u0432\u0438\u044f \u044d\u043a\u0441\u043f\u043b\u0443\u0430\u0442\u0430\u0446\u0438\u0438 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": null,
  "\u041f\u0440\u043e\u0447\u0430\u044f \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u044f": null,
  "\u0421\u0432\u044f\u0437\u044c \u0441 \u0438\u043d\u0446\u0438\u0434\u0435\u043d\u0442\u0430\u043c\u0438 \u0418\u0411": "\u0414\u0430\u043d\u043d\u044b\u0435 \u0443\u0442\u043e\u0447\u043d\u044f\u044e\u0442\u0441\u044f",
  "\u0421\u043e\u0441\u0442\u043e\u044f\u043d\u0438\u0435 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u041e\u043f\u0443\u0431\u043b\u0438\u043a\u043e\u0432\u0430\u043d\u0430",
  "\u0421\u043f\u043e\u0441\u043e\u0431 \u0443\u0441\u0442\u0440\u0430\u043d\u0435\u043d\u0438\u044f": "\u041e\u0431\u043d\u043e\u0432\u043b\u0435\u043d\u0438\u0435 \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u043d\u043e\u0433\u043e \u043e\u0431\u0435\u0441\u043f\u0435\u0447\u0435\u043d\u0438\u044f",
  "\u0421\u043f\u043e\u0441\u043e\u0431 \u044d\u043a\u0441\u043f\u043b\u0443\u0430\u0442\u0430\u0446\u0438\u0438": "\u041d\u0435\u0441\u0430\u043d\u043a\u0446\u0438\u043e\u043d\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u044b\u0439 \u0441\u0431\u043e\u0440 \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u0438",
  "\u0421\u0441\u044b\u043b\u043a\u0438 \u043d\u0430 \u0438\u0441\u0442\u043e\u0447\u043d\u0438\u043a\u0438": "https://git.kernel.org/stable/c/0c67c37e1710b2a8f61c8a02db95a51fe577e2c1\t\nhttps://git.kernel.org/stable/c/60db11f1b7fba4a66b117ea998d965818784a98d\t\nhttps://lore.kernel.org/linux-cve-announce/2025040132-CVE-2025-21896-395c@gregkh/\nhttps://security-tracker.debian.org/tracker/CVE-2025-21896\nhttps://vuldb.com/ru/?id.302619",
  "\u0421\u0442\u0430\u0442\u0443\u0441 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u041f\u043e\u0434\u0442\u0432\u0435\u0440\u0436\u0434\u0435\u043d\u0430 \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0438\u0442\u0435\u043b\u0435\u043c",
  "\u0422\u0438\u043f \u041f\u041e": "\u041e\u043f\u0435\u0440\u0430\u0446\u0438\u043e\u043d\u043d\u0430\u044f \u0441\u0438\u0441\u0442\u0435\u043c\u0430",
  "\u0422\u0438\u043f \u043e\u0448\u0438\u0431\u043a\u0438 CWE": "CWE-200",
  "\u0423\u0440\u043e\u0432\u0435\u043d\u044c \u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438 \u0443\u044f\u0437\u0432\u0438\u043c\u043e\u0441\u0442\u0438": "\u041d\u0438\u0437\u043a\u0438\u0439 \u0443\u0440\u043e\u0432\u0435\u043d\u044c \u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438 (\u0431\u0430\u0437\u043e\u0432\u0430\u044f \u043e\u0446\u0435\u043d\u043a\u0430 CVSS 2.0 \u0441\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u0442 2,7)\n\u041d\u0438\u0437\u043a\u0438\u0439 \u0443\u0440\u043e\u0432\u0435\u043d\u044c \u043e\u043f\u0430\u0441\u043d\u043e\u0441\u0442\u0438 (\u0431\u0430\u0437\u043e\u0432\u0430\u044f \u043e\u0446\u0435\u043d\u043a\u0430 CVSS 3.0 \u0441\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u0442 3,5)"
}

CVE-2025-21896 (GCVE-0-2025-21896)

Vulnerability from cvelistv5 – Published: 2025-04-01 15:26 – Updated: 2026-08-05 11:55

Title

fuse: revert back to __readahead_folio() for readahead

Summary

In the Linux kernel, the following vulnerability has been resolved: fuse: revert back to __readahead_folio() for readahead In commit 3eab9d7bc2f4 ("fuse: convert readahead to use folios"), the logic was converted to using the new folio readahead code, which drops the reference on the folio once it is locked, using an inferred reference on the folio. Previously we held a reference on the folio for the entire duration of the readpages call. This is fine, however for the case for splice pipe responses where we will remove the old folio and splice in the new folio (see fuse_try_move_page()), we assume that there is a reference held on the folio for ap->folios, which is no longer the case. To fix this, revert back to __readahead_folio() which allows us to hold the reference on the folio for the duration of readpages until either we drop the reference ourselves in fuse_readpages_end() or the reference is dropped after it's replaced in the page cache in the splice case. This will fix the UAF bug that was reported.

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 mitre root

References

2 references

URL	Tags
https://git.kernel.org/stable/c/60db11f1b7fba4a66…
https://git.kernel.org/stable/c/0c67c37e1710b2a8f…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 3eab9d7bc2f4ae7f3f9c9c7852ff61600df79856 , < 60db11f1b7fba4a66b117ea998d965818784a98d (git) Affected: 3eab9d7bc2f4ae7f3f9c9c7852ff61600df79856 , < 0c67c37e1710b2a8f61c8a02db95a51fe577e2c1 (git)
Linux	Linux	Affected: 6.13 Unaffected: 0 , < 6.13 (semver) Unaffected: 6.13.6 , ≤ 6.13.* (semver) Unaffected: 6.14 , ≤ * (original_commit_for_fix)

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{
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      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/fuse/dev.c",
            "fs/fuse/file.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "60db11f1b7fba4a66b117ea998d965818784a98d",
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              "version": "3eab9d7bc2f4ae7f3f9c9c7852ff61600df79856",
              "versionType": "git"
            },
            {
              "lessThan": "0c67c37e1710b2a8f61c8a02db95a51fe577e2c1",
              "status": "affected",
              "version": "3eab9d7bc2f4ae7f3f9c9c7852ff61600df79856",
              "versionType": "git"
            }
          ]
        },
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          "product": "Linux",
          "programFiles": [
            "fs/fuse/dev.c",
            "fs/fuse/file.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.13"
            },
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              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
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              "version": "6.13.6",
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              "version": "6.14",
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            }
          ]
        }
      ],
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            {
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                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.13.6",
                  "versionStartIncluding": "6.13",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
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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\nfuse: revert back to __readahead_folio() for readahead\n\nIn commit 3eab9d7bc2f4 (\"fuse: convert readahead to use folios\"), the\nlogic was converted to using the new folio readahead code, which drops\nthe reference on the folio once it is locked, using an inferred\nreference on the folio. Previously we held a reference on the folio for\nthe entire duration of the readpages call.\n\nThis is fine, however for the case for splice pipe responses where we\nwill remove the old folio and splice in the new folio (see\nfuse_try_move_page()), we assume that there is a reference held on the\nfolio for ap-\u003efolios, which is no longer the case.\n\nTo fix this, revert back to __readahead_folio() which allows us to hold\nthe reference on the folio for the duration of readpages until either we\ndrop the reference ourselves in fuse_readpages_end() or the reference is\ndropped after it\u0027s replaced in the page cache in the splice case.\nThis will fix the UAF bug that was reported."
        }
      ],
      "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 bug is reached by mounting a FUSE filesystem and reading a file on it, with the attacker-controlled userspace FUSE server replying over /dev/fuse; this requires local system access (mount + syscalls), not network reachability.\nAC:L - The attacker controls both halves of the trigger \u2014 their own FUSE daemon chooses SPLICE_F_MOVE splice replies with page-aligned stealable buffers, and their own reader process drives readahead \u2014 making the refcount underflow deterministic rather than racy.\nPR:L - Only an unprivileged local account is needed: fuse_fs_type sets FS_USERNS_MOUNT so FUSE can be mounted inside an unprivileged user namespace (unshare -Urm), and distros also ship setuid fusermount3 for direct unprivileged mounts.\nUI:N - The attacker\u0027s own processes perform both the mount/server role and the file read; no action by any other user is required.\nS:U - The corruption stays within the kernel\u0027s own security authority \u2014 standard local kernel memory corruption with no VM, IOMMU, or hypervisor boundary crossed.\nC:H - The over-decremented folio is returned to the page allocator while still referenced by ap-\u003efolios[] and potentially the LRU, so it can be reallocated to another security context and its contents read back through the stale mapping \u2014 an arbitrary kernel/page-cache read primitive.\nI:H - fuse_readpages_end() writes folio flags (folio_end_read) into the already-freed and possibly reallocated page, and the extra folio_put() constitutes a double free \u2014 a page-level UAF that is groomable into an arbitrary write and control-flow hijack.\nA:H - In practice this produced refcount-underflow BUG splats and kernel oopses for ordinary users (Arch and openSUSE crash reports), and the UAF/double-free reliably panics the machine."
            }
          ]
        }
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        "dateUpdated": "2026-08-05T11:55:13.304Z",
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        "shortName": "Linux"
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        {
          "url": "https://git.kernel.org/stable/c/0c67c37e1710b2a8f61c8a02db95a51fe577e2c1"
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    "assignerShortName": "Linux",
    "cveId": "CVE-2025-21896",
    "datePublished": "2025-04-01T15:26:49.200Z",
    "dateReserved": "2024-12-29T08:45:45.783Z",
    "dateUpdated": "2026-08-05T11:55:13.304Z",
    "state": "PUBLISHED"
  },
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}

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.
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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.

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