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NVD / CVE Program· CNA mozilla

CVE-2020-6821: When reading from areas partially or fully outside the source resource with WebGL's <code>copyTexSubImage</code> method, the specification…

HighCVSS 7.5 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 30/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.5% (FIRST EPSS); higher than 74.6% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
  • Fixed version: firefox-esr (Alpine:v3.11) 68.7.0-r0; firefox (Alpine:v3.12) 75.0-r0; mozjs68 (Alpine:v3.12) 68.7.0-r0.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to firefox-esr (Alpine:v3.11) 68.7.0-r0; firefox (Alpine:v3.12) 75.0-r0; mozjs68 (Alpine:v3.12) 68.7.0-r0 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

When reading from areas partially or fully outside the source resource with WebGL's <code>copyTexSubImage</code> method, the specification requires the returned values be zero. Previously, this memory was uninitialized, leading to potentially sensitive data disclosure. This vulnerability affects Thunderbird < 68.7.0, Firefox ESR < 68.7, and Firefox < 75.

Published
Apr 24, 2020
Updated
Jun 16, 2026
EPSS
1.5% · 74th percentile

Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.5%

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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Follow CVE-2020-6821

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  • when exploit code appears or is weaponized
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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
mozillafirefox
mozillafirefox esr
mozillathunderbird

Versions reported by the vendor

Affected version ranges reported by the assigning authority (mozilla). Independent of NVD's CPE analysis and usually ahead of it.

  • Mozilla Firefox

    • unspecified and later · before 75affected

  • Mozilla Firefox ESR

    • unspecified and later · before 68.7affected

  • Mozilla Thunderbird

    • unspecified and later · before 68.7.0affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • mozilla firefoxbefore 75.0
  • mozilla firefox esrbefore 68.7.0
  • mozilla thunderbirdbefore 68.7.0

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Alpine:v3.11firefox-esrbefore 68.7.0-r068.7.0-r0
Alpine:v3.12firefoxbefore 75.0-r075.0-r0
Alpine:v3.12mozjs68before 68.7.0-r068.7.0-r0
Alpine:v3.16thunderbirdbefore 68.7.0-r068.7.0-r0
Alpine:v3.21librewolfbefore 75.0-r075.0-r0
Debian:10firefox-esrbefore 68.7.0esr-1~deb10u168.7.0esr-1~deb10u1
Debian:10thunderbirdbefore 1:68.7.0-1~deb10u11:68.7.0-1~deb10u1
Debian:12firefox-esrbefore 68.7.0esr-168.7.0esr-1
Debian:12thunderbirdbefore 1:68.7.0-11:68.7.0-1
Debian:8firefox-esrbefore 68.7.0esr-1~deb8u168.7.0esr-1~deb8u1
Debian:8thunderbirdbefore 1:68.7.0-1~deb8u11:68.7.0-1~deb8u1
Debian:9firefox-esrbefore 68.7.0esr-1~deb9u168.7.0esr-1~deb9u1
Debian:9thunderbirdbefore 1:68.7.0-1~deb9u11:68.7.0-1~deb9u1
openSUSE:Leap 15.1MozillaFirefoxbefore 68.7.0-lp151.2.42.168.7.0-lp151.2.42.1
openSUSE:Leap 15.1MozillaThunderbirdbefore 68.7.0-lp151.2.35.168.7.0-lp151.2.35.1
openSUSE:Leap 15.1MozillaThunderbirdbefore 68.7.0-lp151.2.31.168.7.0-lp151.2.31.1
Red Hat:enterprise_linux:6::clientfirefoxbefore 0:68.7.0-2.el6_100:68.7.0-2.el6_10
Red Hat:enterprise_linux:6::clientfirefox-debuginfobefore 0:68.7.0-2.el6_100:68.7.0-2.el6_10
Red Hat:enterprise_linux:6::clientthunderbirdbefore 0:68.7.0-1.el6_100:68.7.0-1.el6_10
Red Hat:enterprise_linux:6::clientthunderbird-debuginfobefore 0:68.7.0-1.el6_100:68.7.0-1.el6_10
Red Hat:enterprise_linux:7::clientfirefoxbefore 0:68.7.0-2.el7_80:68.7.0-2.el7_8
Red Hat:enterprise_linux:7::clientfirefox-debuginfobefore 0:68.7.0-2.el7_80:68.7.0-2.el7_8
Red Hat:enterprise_linux:7::clientthunderbirdbefore 0:68.7.0-1.el7_80:68.7.0-1.el7_8
Red Hat:enterprise_linux:7::clientthunderbird-debuginfobefore 0:68.7.0-1.el7_80:68.7.0-1.el7_8

+16

Same product

mozilla: all records

Other highest-scoring records for the same primary product.

  • CVE-2010-3765Mozilla Firefox 3.5.x through 3.5.14 and 3.6.x through 3.6.11, Thunderbird 3.1.6 before 3.1.6 and 3.0.x before 3.0.10, and SeaMonkey 2.x…KEV
    94Now
  • CVE-2019-11708Insufficient vetting of parameters passed with the Prompt:Open IPC message between child and parent processes can result in the…KEV
    87Now
  • CVE-2015-4495The PDF reader in Mozilla Firefox before 39.0.3, Firefox ESR 38.x before 38.1.1, and Firefox OS before 2.2 allows remote attackers to…KEV
    86Now

Published before and after this one in the same product

  • ← EarlierCVE-2020-6819Apr 24, 2020 · Under certain conditions, when running the nsDocShell destructor, a race condition can cause a use-after-free.KEV
    63This week
  • ← EarlierCVE-2020-6820Apr 24, 2020 · Under certain conditions, when handling a ReadableStream, a race condition can cause a use-after-free.KEV
    64This week
  • Later →CVE-2020-6822Apr 24, 2020 · On 32-bit builds, an out of bounds write could have occurred when processing an image larger than 4 GB in <code>GMPDecodeData</code>.
    35Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
alpine:firefox75.0-r0 · Alpine:v3.12Package registry (OSV)
alpine:firefox-esr68.7.0-r0 · Alpine:v3.11Package registry (OSV)
alpine:librewolf75.0-r0 · Alpine:v3.21Package registry (OSV)
alpine:mozjs6868.7.0-r0 · Alpine:v3.12Package registry (OSV)
alpine:thunderbird68.7.0-r0 · Alpine:v3.16Package registry (OSV)
debian:firefox-esr68.7.0esr-1 · Debian:12Package registry (OSV)
debian:thunderbird1:68.7.0-1 · Debian:12Package registry (OSV)
opensuse:MozillaFirefox68.7.0-lp151.2.42.1 · openSUSE:Leap 15.1Package registry (OSV)
opensuse:MozillaThunderbird68.7.0-lp151.2.31.1 · openSUSE:Leap 15.1Package registry (OSV)
red hat:firefox0:68.7.0-2.el8_0 · Red Hat:rhel_e4s:8.0::appstreamPackage registry (OSV)
red hat:firefox-debuginfo0:68.7.0-2.el8_0 · Red Hat:rhel_e4s:8.0::appstreamPackage registry (OSV)
red hat:firefox-debugsource0:68.7.0-2.el8_0 · Red Hat:rhel_e4s:8.0::appstreamPackage registry (OSV)
red hat:thunderbird0:68.7.0-1.el6_10 · Red Hat:enterprise_linux:6::clientPackage registry (OSV)
red hat:thunderbird-debuginfo0:68.7.0-1.el6_10 · Red Hat:enterprise_linux:6::clientPackage registry (OSV)
red hat:thunderbird-debugsource0:68.7.0-1.el8_1 · Red Hat:enterprise_linux:8::appstreamPackage registry (OSV)
suse:MozillaFirefox68.7.0-3.84.2 · SUSE:Linux Enterprise Module for Desktop Applications 15 SP1Package registry (OSV)
suse:MozillaThunderbird68.7.0-3.77.1 · SUSE:Linux Enterprise Workstation Extension 15 SP1Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
none
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-908 · Use of Uninitialized Resource

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records