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CVE-2026-6785

Memory safety bugs fixed in Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird ESR 140.10, Firefox 150 and Thunderbird 150

HIGH
7.5
CVSS Score
Published: April 21, 2026 at 12:41 PM UTC
Updated: October 26, 2026 at 12:10 AM UTC
3 products affected across 2 vendorsFirefoxThunderbirdEnterprise Linux

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Severity
HIGH7.5
Exploit prediction
EPSS 0.5%
SSVC
No known exploit

Description

Memory safety bugs present in Firefox ESR 115.34, Firefox ESR 140.9, Thunderbird ESR 140.9, Firefox 149 and Thunderbird 149. 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 was fixed in Firefox 150, Firefox ESR 115.35, and Firefox ESR 140.10.

Affected

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

Firefox· Mozilla
95%
v < 115.35.0v < 150.0140.0 ≤ v < 140.10.0
Vendor states this is fixed in 115.35 (unaffected)
Affected range stops below 115.35.0, so it looks safe — our inference, not a vendor statement
Vendor states this is fixed in 140.10 (unaffected)
Affected range stops below 140.10.0, so it looks safe — our inference, not a vendor statement
Vendor states this is fixed in 150 (unaffected)
Affected range stops below 150.0, so it looks safe — our inference, not a vendor statement
Thunderbird· Mozilla
95%
140.0 ≤ v < 140.10.0
Vendor states this is fixed in 140.10 (unaffected)
Affected range stops below 140.10.0, so it looks safe — our inference, not a vendor statement
Vendor states this is fixed in 150 (unaffected)
Enterprise Linux· Red Hatrpm
60%
10
Vendor states this is fixed in 0:140.10.0-1.el10_0 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el10_1 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el10_2 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el8_10 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el8_4 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el8_6 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el8_8 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el9_0 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el9_2 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el9_4 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el9_6 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el9_7 (unaffected)
Vendor states this is fixed in 0:140.10.0-1.el9_8 (unaffected)
Vendor states this is fixed in 0:140.10.0-2.el7_9 (unaffected)
Vendor states this is fixed in 0:140.10.1-1.el9_8 (unaffected)
Vendor states this is fixed in 6 (unknown)
Vendor states this is fixed in 7 (unknown)

References (36)

Broken Link
Source: cverecord
https://bugzilla.mozilla.org/buglist.cgi?bug_id=1935995%2C1999158%2C2015952%2C2021909%2C2022026%2C2022041%2C2022088%2C2022276%2C2022335%2C2022338%2C2022373%2C2022597%2C2022874%2C2023276%2C2023544%2C2023551%2C2023599%2C2023608%2C2023814%2C2024233%2C2024239%2C2024241%2C2024242%2C2024250%2C2024251%2C2024343%2C2024422%2C2024425%2C2024440%2C2024442%2C2024446%2C2024458%2C2024463%2C2024478%2C2024650%2C2024653%2C2024654%2C2024655%2C2024656%2C2024661%2C2024662%2C2024668%2C2024919%2C2025278%2C2025349%2C2025350%2C2025354%2C2025360%2C2025363%2C2025370%2C2025379%2C2025381%2C2025399%2C2025400%2C2025403%2C2025407%2C2025415%2C2025420%2C2025427%2C2025429%2C2025430%2C2025479%2C2025489%2C2025493%2C2025497%2C2025502%2C2025515%2C2025517%2C2025526%2C2025609%2C2025948%2C2025949%2C2025951%2C2025953%2C2025955%2C2025962%2C2025969%2C2025970%2C2025971%2C2025973%2C2025976%2C2025977%2C2026280%2C2026285%2C2026293%2C2026296%2C2026310%2C2027237%2C2027260%2C2027268%2C2027277%2C2027284%2C2027291%2C2027293%2C2027298%2C2027330%2C2027342%2C2027345%2C2027359%2C2027365%2C2027378%2C2027754%2C2027959%2C2027962%2C2027964%2C2027971%2C2027974%2C2027979%2C2027982%2C2027995%2C2028001%2C2028267%2C2028268%2C2028275%2C2028288%2C2028290%2C2028291%2C2028528%2C2028551%2C2028627%2C2028879%2C2028889%2C2029061%2C2029071%2C2029283%2C2029296%2C2029314%2C2029323%2C2029411%2C2029423%2C2029424%2C2029425%2C2029427%2C2029436%2C2029440%2C2029449%2C2029450%2C2029458%2C2029462%2C2029468%2C2029472%2C2029690%2C2029707%2C2029708%2C2029728%2C2029802%2C2029896%2C2029906%2C2030106%2C2030118%2C2030123%2C2030135%2C2030230%2C2030320
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-30/
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-31/
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-32/
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-33/
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-34/
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://access.redhat.com/errata/RHSA-2026:10757
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://access.redhat.com/errata/RHSA-2026:10766

SSVC — Action Prioritization

SSVCNo known exploitNot automatableTotal impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHCISA-ADP
Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-125CWE-416CWE-787

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