This report was translated by AI; nobody has reviewed the translation yet. Original language: Slovak.

[TLP:CLEAR] Mozilla fixes 58 vulnerabilities

Mozilla fixes 58 vulnerabilities in various products. The most severe vulnerabilities are listed below. Individual products and their fixed versions: Firefox - 154 [1] Firefox ESR - 153.1, 140.14, 115.39 [2][3][4] Thunderbird - 154 [5] Thunderbird ESR - 153.1, 140.14 [6][7]

Mozilla Firefox, Thunderbird - sandbox escape (CVE-2026-75874)
CVSS 10.0 (Critical)

An unauthenticated remote attacker can escape the sandbox in the Remote Settings Client component [1][5].

The vulnerability is present in products:

  • Firefox; <154
  • Thunderbird; <154

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

More information:

The vulnerability was publicly disclosed 18. 8. 2026.

Mozilla Firefox, Firefox ESR, Thunderbird, Thunderbird ESR - privilege escalation (CVE-2026-74946)
CVSS 8.8 (High)

Due to incorrect memory buffer boundary checks in the Graphics: CanvasWebGL component, an unauthenticated remote attacker can gain elevated privileges after user interaction [1][2][3][4][5][6][7].

The vulnerability is present in products:

  • Mozilla Firefox; <154
  • Mozilla Firefox ESR; >=115, <115.39; >=140, <140.14; >=153, <153.1
  • Mozilla Thunderbird; <154
  • Mozilla Thunderbird ESR; >=140, <140.14; >=153, <153.1

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

More information:

  • CVE-2026-74946 at cve.org, NVD
  • CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer at cwe.mitre.org

The vulnerability was publicly disclosed 18. 8. 2026.

Mozilla Firefox, Firefox ESR, Thunderbird, Thunderbird ESR - privilege escalation (CVE-2026-74947)
CVSS 8.8 (High)

Due to freeing of an invalid pointer in the Graphics component, an unauthenticated remote attacker can gain elevated privileges after user interaction [1][4][5][7].

The vulnerability is present in products:

  • Mozilla Firefox; <154
  • Mozilla Firefox ESR; >=153, <153.1
  • Mozilla Thunderbird; <154;
  • Mozilla Thunderbird ESR; >=153, <153.1

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

More information:

The vulnerability was publicly disclosed 18. 8. 2026.

Mozilla Firefox, Firefox ESR, Thunderbird, Thunderbird ESR - privilege escalation (CVE-2026-74949)
CVSS 8.8 (High)

Due to a use-after-free in the Graphics: Canvas2D component, an unauthenticated remote attacker can gain elevated privileges after user interaction [1][3][4][5][6][7].

The vulnerability is present in products:

  • Mozilla Firefox; <154
  • Mozilla Firefox ESR; >=140, <140.14; >=153, <153.1
  • Mozilla Thunderbird; <154
  • Mozilla Thunderbird ESR; >=140, <140.14; >=153, <153.1

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

More information:

By CESNET, z.s.p.o. Henrieta Paločková on 19. 8. 2026.

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