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01 Record

CVE-2020-6819

Under certain conditions, when running the nsDocShell destructor, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability

HighKEVPUBLISHEDCNA: mozilla
CNA base score8.1 CVSS v3.xCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

02 Description

Under certain conditions, when running the nsDocShell destructor, a race condition can cause a use-after-free. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability

03 Exploitation and scoring

Exploitation
Exploited in the wild. Listed in the CISA Known Exploited Vulnerabilities catalog on 2021-11-03. Federal remediation due 2022-05-03.
SSVC decision
  • ExploitationactiveCISA reports credible evidence of active exploitation.
  • AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
  • Technical ImpacttotalSuccessful exploitation gives total control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
3.03% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 87.2% of scored records. A rank, not a probability.
NVD base score
8.1 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD analysis status
Analyzed. NVD last modified this record on 2026-06-17.
Red Hat severity
Critical. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2020-04-24 15:56Z6 YR AGO
Last updated
2025-10-21 23:35Z1 YR AGO
Reserved
2020-01-10
Assigning CNA
mozilla
Record state
PUBLISHED
Severity
High (CVSS 8.1)
CNA CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Weaknesses
  • CWE-416Use After FreeVariant
  • CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')Class
Data version
5.1
Document digest
09d340da559f7ed700f43331249993c6ede638f22e5e042440cf5eeff6f10fe2

05 Affected products

VendorProductVersionsPlatforms
MozillaThunderbird< 68.7.0—
MozillaFirefox< 74.0.1—
MozillaFirefox ESR< 68.6.1—

06 References

07 Fixed in

Arch Linux

  • firefox
    Fixed in 74.0.1-1
  • thunderbird
    Fixed in 68.7.0-1

Source: Arch Linux Security Tracker, the Arch Linux security team. Reformatted by exploit.cc.

Debian 12

  • firefox-esr
    Fixed in 68.6.1esr-1
  • thunderbird
    Fixed in 1:68.7.0-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 13

  • firefox-esr
    Fixed in 68.6.1esr-1
  • thunderbird
    Fixed in 1:68.7.0-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Debian 14

  • firefox-esr
    Fixed in 68.6.1esr-1
  • thunderbird
    Fixed in 1:68.7.0-1

Source: Debian Security Tracker, the Debian security team. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 16.04 LTS

  • firefox
    Fixed in 74.0.1+build1-0ubuntu0.16.04.1
  • thunderbird
    Fixed in 1:68.7.0+build1-0ubuntu0.16.04.2

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 18.04 LTS

  • firefox
    Fixed in 74.0.1+build1-0ubuntu0.18.04.1
  • thunderbird
    Fixed in 1:68.7.0+build1-0ubuntu0.18.04.1

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

Ubuntu 20.04 LTS

  • firefox
    Fixed in 75.0+build3-0ubuntu1
  • thunderbird
    Fixed in 1:68.7.0+build1-0ubuntu1

Source: Ubuntu, Canonical Ltd. Licensed under CC BY-SA 4.0. Received through OSV.dev. Reformatted by exploit.cc.

A release or ecosystem missing from this list has no record here. It may be unaffected or not covered by the source. Source notices and licences.