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CVE-2021-43534

HIGH
8.8
CVSS Score
Published: December 8, 2021 at 09:20 PM UTC
Updated: June 17, 2026 at 04:11 AM UTC
4 products affected across 2 vendorsDebian LinuxFirefoxThunderbird

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Severity
HIGH8.8
Exploit prediction
EPSS 1%

Description

Mozilla developers and community members reported memory safety bugs present in Firefox 93 and Firefox ESR 91.2. Some of these bugs showed evidence of memory corruption and we presume that with enough effort some of these could have been exploited to run arbitrary code. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Debian Linux· Debiandrupal
95%
10.011.09.0
Firefox· Mozilla
95%
v < 94
Affected range stops below 94, so it looks safe — our inference, not a vendor statement
Affected range stops below 94.0, so it looks safe — our inference, not a vendor statement
Firefox ESR· Mozilla
95%
v < 91.3
Affected range stops below 91.3, so it looks safe — our inference, not a vendor statement
Affected range stops below 91.3.0, so it looks safe — our inference, not a vendor statement
Thunderbird· Mozilla
95%
v < 91.3
Affected range stops below 91.3, so it looks safe — our inference, not a vendor statement
Affected range stops below 91.3.0, so it looks safe — our inference, not a vendor statement

References (8)

x_refsource_MISCBroken LinkIssue TrackingVendor Advisory
Source: [email protected]
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1606864%2C1712671%2C1730048%2C1735152
Mailing Listx_refsource_MLISTThird Party Advisory
Source: [email protected]
https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html
Mailing Listx_refsource_MLISTThird Party Advisory
Source: [email protected]
https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html
Vendor Advisoryx_refsource_DEBIANThird Party Advisory
Source: [email protected]
https://www.debian.org/security/2021/dsa-5026
Vendor Advisoryx_refsource_DEBIANIssue TrackingThird Party Advisory
Source: [email protected]
https://www.debian.org/security/2022/dsa-5034
x_refsource_MISCVendor Advisory
Source: [email protected]
https://www.mozilla.org/security/advisories/mfsa2021-48/
x_refsource_MISCVendor Advisory
Source: [email protected]
https://www.mozilla.org/security/advisories/mfsa2021-49/
x_refsource_MISCVendor Advisory
Source: [email protected]
https://www.mozilla.org/security/advisories/mfsa2021-50/

CVSS

8.8HIGH[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-787

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