Vulnerability-Lookup

BDU:2026-14096 (CVE-2026-40684)

Vulnerability from fstec – Published: 2026-09-04 – Updated: 2026-09-04 – View on bdu.fstec.ru Fixed

Title

Уязвимость функции dn_expand() почтового сервера Exim, позволяющая нарушителю получить несанкционированный доступ к защищаемой информации

Summary

Уязвимость функции dn_expand() почтового сервера Exim связана с ошибками представления заданных функций. Эксплуатация уязвимости может позволить нарушителю, действующему удаленно, получить несанкционированный доступ к защищаемой информации

Severity

7.8 (High) CVSS 2.0


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

7.5 (High) CVSS 3.1


                      
                        CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Class

Code vulnerability

Status

Confirmed by the vendor

Exploitation

Functionality abuse

Incidents

Being clarified

Remediation

Software update

CWE

CWE-684 - Некорректное представление заданных функций

Aliases

CVE-2026-40684

References

9 references

URL
https://github.com/advisories/GHSA-q496-q274-jgh9
http://www.openwall.com/lists/oss-security/2026/05/01/11
https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81
https://exim.org/static/doc/security/CVE-2025-40684.txt
https://exim.org/static/doc/security/CVE-2026-40684.txt
https://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessment
https://www.openwall.com/lists/oss-security/2026/04/30/21
https://redos.red-soft.ru/search/?iblock_id=&q=CVE-2026-40684
https://security-tracker.debian.org/tracker/CVE-2026-40684

Impacted products

3 products from 3 vendors

Vendors

Сообщество свободного программного обеспечения, ООО «Ред Софт», GNU General Public License

Products

Debian GNU/Linux, РЕД ОС (запись в едином реестре российских программ №3751), exim

Versions

12 (Debian GNU/Linux), 7.3 (РЕД ОС), 13 (Debian GNU/Linux), 8.0 (РЕД ОС), до 4.99.2 (exim)

Product types

Operating system, Network software

Platforms

Сообщество свободного программного обеспечения Debian GNU/Linux 12, ООО «Ред Софт» РЕД ОС 7.3 (запись в едином реестре российских программ №3751), Сообщество свободного программного обеспечения Debian GNU/Linux 13, ООО «Ред Софт» РЕД ОС 8.0 (запись в едином реестре российских программ №3751)

Mitigations

Использование рекомендаций производителя: https://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81 https://github.com/advisories/GHSA-q496-q274-jgh9 Для Ред ОС: https://redos.red-soft.ru/search/?iblock_id=&q=CVE-2026-40684 Для Debian GNU/Linux: https://security-tracker.debian.org/tracker/CVE-2026-40684

JSON

To clipboard

{
  "CVSS 2.0": "AV:N/AC:L/Au:N/C:N/I:N/A:C",
  "CVSS 3.0": "AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
  "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, \u041e\u041e\u041e \u00ab\u0420\u0435\u0434 \u0421\u043e\u0444\u0442\u00bb, GNU General Public License",
  "\u0412\u0435\u0440\u0441\u0438\u044f \u041f\u041e": "12 (Debian GNU/Linux), 7.3 (\u0420\u0415\u0414 \u041e\u0421), 13 (Debian GNU/Linux), 8.0 (\u0420\u0415\u0414 \u041e\u0421), \u0434\u043e 4.99.2 (exim)",
  "\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": "\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 \u043f\u0440\u043e\u0438\u0437\u0432\u043e\u0434\u0438\u0442\u0435\u043b\u044f:\nhttps://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81\nhttps://github.com/advisories/GHSA-q496-q274-jgh9\n\n\u0414\u043b\u044f \u0420\u0435\u0434 \u041e\u0421:\nhttps://redos.red-soft.ru/search/?iblock_id=\u0026q=CVE-2026-40684\n\n\u0414\u043b\u044f Debian GNU/Linux:\nhttps://security-tracker.debian.org/tracker/CVE-2026-40684",
  "\u0414\u0430\u0442\u0430 \u0432\u044b\u044f\u0432\u043b\u0435\u043d\u0438\u044f": "30.04.2026",
  "\u0414\u0430\u0442\u0430 \u043f\u043e\u0441\u043b\u0435\u0434\u043d\u0435\u0433\u043e \u043e\u0431\u043d\u043e\u0432\u043b\u0435\u043d\u0438\u044f": "04.09.2026",
  "\u0414\u0430\u0442\u0430 \u043f\u0443\u0431\u043b\u0438\u043a\u0430\u0446\u0438\u0438": "04.09.2026",
  "\u0418\u0434\u0435\u043d\u0442\u0438\u0444\u0438\u043a\u0430\u0442\u043e\u0440": "BDU:2026-14096",
  "\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-2026-40684",
  "\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, \u0420\u0415\u0414 \u041e\u0421 (\u0437\u0430\u043f\u0438\u0441\u044c \u0432 \u0435\u0434\u0438\u043d\u043e\u043c \u0440\u0435\u0435\u0441\u0442\u0440\u0435 \u0440\u043e\u0441\u0441\u0438\u0439\u0441\u043a\u0438\u0445 \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c \u21163751), exim",
  "\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 12 , \u041e\u041e\u041e \u00ab\u0420\u0435\u0434 \u0421\u043e\u0444\u0442\u00bb \u0420\u0415\u0414 \u041e\u0421 7.3  (\u0437\u0430\u043f\u0438\u0441\u044c \u0432 \u0435\u0434\u0438\u043d\u043e\u043c \u0440\u0435\u0435\u0441\u0442\u0440\u0435 \u0440\u043e\u0441\u0441\u0438\u0439\u0441\u043a\u0438\u0445 \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c \u21163751), \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 13 , \u041e\u041e\u041e \u00ab\u0420\u0435\u0434 \u0421\u043e\u0444\u0442\u00bb \u0420\u0415\u0414 \u041e\u0421 8.0  (\u0437\u0430\u043f\u0438\u0441\u044c \u0432 \u0435\u0434\u0438\u043d\u043e\u043c \u0440\u0435\u0435\u0441\u0442\u0440\u0435 \u0440\u043e\u0441\u0441\u0438\u0439\u0441\u043a\u0438\u0445 \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c \u21163751)",
  "\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 \u0444\u0443\u043d\u043a\u0446\u0438\u0438 dn_expand() \u043f\u043e\u0447\u0442\u043e\u0432\u043e\u0433\u043e \u0441\u0435\u0440\u0432\u0435\u0440\u0430 Exim, \u043f\u043e\u0437\u0432\u043e\u043b\u044f\u044e\u0449\u0430\u044f \u043d\u0430\u0440\u0443\u0448\u0438\u0442\u0435\u043b\u044e \u043f\u043e\u043b\u0443\u0447\u0438\u0442\u044c \u043d\u0435\u0441\u0430\u043d\u043a\u0446\u0438\u043e\u043d\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u044b\u0439 \u0434\u043e\u0441\u0442\u0443\u043f \u043a \u0437\u0430\u0449\u0438\u0449\u0430\u0435\u043c\u043e\u0439 \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u0438",
  "\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": "\u041d\u0435\u043a\u043e\u0440\u0440\u0435\u043a\u0442\u043d\u043e\u0435 \u043f\u0440\u0435\u0434\u0441\u0442\u0430\u0432\u043b\u0435\u043d\u0438\u0435 \u0437\u0430\u0434\u0430\u043d\u043d\u044b\u0445 \u0444\u0443\u043d\u043a\u0446\u0438\u0439 (CWE-684)",
  "\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 \u0444\u0443\u043d\u043a\u0446\u0438\u0438 dn_expand() \u043f\u043e\u0447\u0442\u043e\u0432\u043e\u0433\u043e \u0441\u0435\u0440\u0432\u0435\u0440\u0430 Exim \u0441\u0432\u044f\u0437\u0430\u043d\u0430 \u0441 \u043e\u0448\u0438\u0431\u043a\u0430\u043c\u0438 \u043f\u0440\u0435\u0434\u0441\u0442\u0430\u0432\u043b\u0435\u043d\u0438\u044f \u0437\u0430\u0434\u0430\u043d\u043d\u044b\u0445 \u0444\u0443\u043d\u043a\u0446\u0438\u0439. \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, \u043f\u043e\u043b\u0443\u0447\u0438\u0442\u044c \u043d\u0435\u0441\u0430\u043d\u043a\u0446\u0438\u043e\u043d\u0438\u0440\u043e\u0432\u0430\u043d\u043d\u044b\u0439 \u0434\u043e\u0441\u0442\u0443\u043f \u043a \u0437\u0430\u0449\u0438\u0449\u0430\u0435\u043c\u043e\u0439 \u0438\u043d\u0444\u043e\u0440\u043c\u0430\u0446\u0438\u0438",
  "\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": "\u0417\u043b\u043e\u0443\u043f\u043e\u0442\u0440\u0435\u0431\u043b\u0435\u043d\u0438\u0435 \u0444\u0443\u043d\u043a\u0446\u0438\u043e\u043d\u0430\u043b\u043e\u043c",
  "\u0421\u0441\u044b\u043b\u043a\u0438 \u043d\u0430 \u0438\u0441\u0442\u043e\u0447\u043d\u0438\u043a\u0438": "https://github.com/advisories/GHSA-q496-q274-jgh9\nhttp://www.openwall.com/lists/oss-security/2026/05/01/11\nhttps://code.exim.org/exim/exim/commit/628bbaca7672748d941a12e7cd5f0122a4e18c81\nhttps://exim.org/static/doc/security/CVE-2025-40684.txt\nhttps://exim.org/static/doc/security/CVE-2026-40684.txt\nhttps://exim.org/static/doc/security/cve-2026-04.1/CVE2026-40684.assessment\nhttps://www.openwall.com/lists/oss-security/2026/04/30/21\nhttps://redos.red-soft.ru/search/?iblock_id=\u0026q=CVE-2026-40684\nhttps://security-tracker.debian.org/tracker/CVE-2026-40684",
  "\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, \u0421\u0435\u0442\u0435\u0432\u043e\u0435 \u043f\u0440\u043e\u0433\u0440\u0430\u043c\u043c\u043d\u043e\u0435 \u0441\u0440\u0435\u0434\u0441\u0442\u0432\u043e",
  "\u0422\u0438\u043f \u043e\u0448\u0438\u0431\u043a\u0438 CWE": "CWE-684",
  "\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": "\u0412\u044b\u0441\u043e\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 7,8)\n\u0412\u044b\u0441\u043e\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 3.1 \u0441\u043e\u0441\u0442\u0430\u0432\u043b\u044f\u0435\u0442 7,5)"
}

CVE-2026-40684 (GCVE-0-2026-40684)

Vulnerability from cvelistv5 – Published: 2026-04-30 00:00 – Updated: 2026-05-01 17:22

Summary

In Exim before 4.99.2, on systems using musl libc (not glibc), an attacker can crash the connection instance when malformed DNS data is present in PTR records. This is caused by a dn_expand oddity in octal printing.

Severity

5.9 (Medium)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-05-01 14:25 UTC

CWE

CWE-684 - Incorrect Provision of Specified Functionality

Assigner

mitre mitre root

References

5 references

URL	Tags
https://www.openwall.com/lists/oss-security/2026/…
https://exim.org/static/doc/security/cve-2026-04.…
https://code.exim.org/exim/exim/commit/628bbaca76…
https://exim.org/static/doc/security/CVE-2026-40684.txt
http://www.openwall.com/lists/oss-security/2026/0…

Impacted products

1 product

Vendor	Product	Version
Exim	Exim	Affected: 0 , < 4.99.2 (semver) cpe:2.3:a:exim:exim::::::::

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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.

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.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

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