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NVD / CVE Program· CNA mozilla

CVE-2021-29987: After requesting multiple permissions, and closing the first permission panel, subsequent permission panels will be displayed in a different

Noroxi assessment

Priority: Monitor (action score 26/100)

  • 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: 0.94% (FIRST EPSS); higher than 61% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
  • Fixed version: MozillaFirefox (openSUSE:Leap 15.2) 91.2.0-lp152.2.67.1; MozillaThunderbird (openSUSE:Leap 15.2) 91.4.0-lp152.2.52.1; rust-cbindgen (openSUSE:Leap 15.2) 0.19.0-lp152.2.7.1.

Low priority for now. Upgrade to MozillaFirefox (openSUSE:Leap 15.2) 91.2.0-lp152.2.67.1; MozillaThunderbird (openSUSE:Leap 15.2) 91.4.0-lp152.2.52.1; rust-cbindgen (openSUSE:Leap 15.2) 0.19.0-lp152.2.7.1 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

After requesting multiple permissions, and closing the first permission panel, subsequent permission panels will be displayed in a different position but still record a click in the default location, making it possible to trick a user into accepting a permission they did not want to. *This bug only affects Firefox on Linux. Other operating systems are unaffected.*. This vulnerability affects Firefox < 91 and Thunderbird < 91.

MediumCVSS 6.5 · v3.1—No exploit Fix available
Published
Aug 17, 2021
Updated
Jun 16, 2026
EPSS
0.9% · 61th percentile

Report tools

JSON

Action score

26

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.9%

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

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2021-29987

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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
mozillathunderbird
linuxlinux kernel

Affected versions

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

  • mozilla firefoxbefore 91.0
  • mozilla thunderbirdbefore 91.0

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 91affected

  • Mozilla Thunderbird

    • unspecified and later · before 91affected

Package-level exposure

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

EcosystemPackageAffected rangeFix
openSUSE:Leap 15.2MozillaFirefoxbefore 91.2.0-lp152.2.67.191.2.0-lp152.2.67.1
openSUSE:Leap 15.2MozillaThunderbirdbefore 91.4.0-lp152.2.52.191.4.0-lp152.2.52.1
openSUSE:Leap 15.2rust-cbindgenbefore 0.19.0-lp152.2.7.10.19.0-lp152.2.7.1
openSUSE:Leap 15.3MozillaFirefoxbefore 91.2.0-8.54.191.2.0-8.54.1
openSUSE:Leap 15.3MozillaFirefox-branding-SLEbefore 91-9.5.191-9.5.1
openSUSE:Leap 15.3MozillaThunderbirdbefore 91.4.0-8.45.291.4.0-8.45.2
openSUSE:Leap 15.3rust-cbindgenbefore 0.19.0-1.9.10.19.0-1.9.1
SUSE:HPE Helion OpenStack 8MozillaFirefoxbefore 91.1.0-112.71.191.1.0-112.71.1
SUSE:HPE Helion OpenStack 8MozillaFirefoxbefore 91.9.0-112.104.191.9.0-112.104.1
SUSE:HPE Helion OpenStack 8MozillaFirefox-branding-SLEbefore 91-35.6.691-35.6.6
SUSE:Linux Enterprise High Performance Computing 15-ESPOSMozillaFirefoxbefore 91.9.0-150000.150.34.191.9.0-150000.150.34.1
SUSE:Linux Enterprise High Performance Computing 15-ESPOSMozillaFirefoxbefore 91.2.0-3.155.291.2.0-3.155.2
SUSE:Linux Enterprise High Performance Computing 15-ESPOSMozillaFirefox-branding-SLEbefore 91-4.19.191-4.19.1
SUSE:Linux Enterprise Module for Desktop Applications 15 SP2MozillaFirefoxbefore 91.2.0-8.54.191.2.0-8.54.1
SUSE:Linux Enterprise Module for Desktop Applications 15 SP2MozillaFirefox-branding-SLEbefore 91-9.5.191-9.5.1
SUSE:Linux Enterprise Server 11 SP4-LTSSMozillaFirefoxbefore 78.14.0-78.140.478.14.0-78.140.4
SUSE:Linux Enterprise Server 11 SP4-LTSSMozillaFirefoxbefore 91.2.0-78.143.191.2.0-78.143.1
SUSE:Linux Enterprise Server 11 SP4-LTSSMozillaFirefox-branding-SLEDbefore 91-21.18.191-21.18.1
SUSE:Linux Enterprise Workstation Extension 15 SP2MozillaThunderbirdbefore 91.4.0-8.45.291.4.0-8.45.2

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 befKEV
    94Now
  • CVE-2019-11708Insufficient vetting of parameters passed with the Prompt:Open IPC message between child and parent processes can result in the non-sandboxeKEV
    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 bypassKEV
    86Now

Published before and after this one in the same product

  • ← EarlierCVE-2021-29985Aug 17, 2021 · A use-after-free vulnerability in media channels could have led to memory corruption and a potentially exploitable crash.
    35Monitor
  • ← EarlierCVE-2021-29986Aug 17, 2021 · A suspected race condition when calling getaddrinfo led to memory corruption and a potentially exploitable crash.
    32Monitor
  • Later →CVE-2021-29988Aug 17, 2021 · Firefox incorrectly treated an inline list-item element as a block element, resulting in an out of bounds read or memory corruption, and a p
    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
opensuse:MozillaFirefox91.2.0-lp152.2.67.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:MozillaFirefox-branding-SLE91-9.5.1 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:MozillaThunderbird91.4.0-lp152.2.52.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:rust-cbindgen0.19.0-lp152.2.7.1 · openSUSE:Leap 15.2Package registry (OSV)
suse:MozillaFirefox78.14.0-78.140.4 · SUSE:Linux Enterprise Server 11 SP4-LTSSPackage registry (OSV)
suse:MozillaFirefox-branding-SLE91-35.6.6 · SUSE:HPE Helion OpenStack 8Package registry (OSV)
suse:MozillaFirefox-branding-SLED91-21.18.1 · SUSE:Linux Enterprise Server 11 SP4-LTSSPackage registry (OSV)
suse:MozillaThunderbird91.4.0-8.45.2 · SUSE:Linux Enterprise Workstation Extension 15 SP2Package 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.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • 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
Required
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-307 · Improper Restriction of Excessive Authentication Attempts

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/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.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (3 more)

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

All records