CVE-2021-23998

MEDIUMNVD 6.56.5—

6.5

Through complicated navigations with new windows, an HTTP page could have inherited a secure lock icon from an HTTPS page. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.

CVSS v3: 6.5
EG Score: 6.5(medium)
EPSS: 37.0%
KEV: Not listed

Published

June 24, 2021

Last Modified

November 21, 2024

References (8)

security@mozillahttps://bugzilla.mozilla.org/show_bug.cgi?id=1667456
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2021-14/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2021-15/
security@mozillahttps://www.mozilla.org/security/advisories/mfsa2021-16/
af854a3a-2127-422b-91ae-364da2661108https://bugzilla.mozilla.org/show_bug.cgi?id=1667456
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2021-14/
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2021-15/
af854a3a-2127-422b-91ae-364da2661108https://www.mozilla.org/security/advisories/mfsa2021-16/

Patch Availability(11)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
ubuntu	xul-ext-lightning (1:78.11.0+build1-0ubuntu0.18.04.2) @ bionic	2026-05-26	ubuntu
ubuntu	firefox-mozsymbols (88.0+build2-0ubuntu0.16.04.1) @ xenial	2026-05-26	ubuntu
ubuntu	xul-ext-lightning (1:78.11.0+build1-0ubuntu0.20.10.2) @ groovy	2026-05-26	ubuntu
redhat	firefox-0:78.10.0-1.el8_2	2021-04-26	redhat
redhat	thunderbird-0:78.10.0-1.el7_9	2021-04-26	redhat
redhat	firefox-0:78.10.0-1.el7_9	2021-04-26	redhat
redhat	thunderbird-0:78.10.0-1.el8_3	2021-04-26	redhat
redhat	firefox-0:78.10.0-1.el8_3	2021-04-26	redhat
redhat	thunderbird-0:78.10.0-1.el8_1	2021-04-26	redhat
redhat	firefox-0:78.10.0-1.el8_1	2021-04-26	redhat
redhat	thunderbird-0:78.10.0-1.el8_2	2021-04-26	redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-345Insufficient Verification of Data Authenticity

Data Freshness Timeline

(refreshed 11× in last 7d / 20× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-06-02 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 14:33 UTCEG score recompute
2026-05-26 14:33 UTCVendor advisory
2026-05-26 14:32 UTCGHSA enrichment
2026-05-26 13:42 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-24 16:49 UTCepss_batch

Frequently asked(5)

What is CVE-2021-23998?

CVE-2021-23998 is a medium vulnerability published on June 24, 2021. Through complicated navigations with new windows, an HTTP page could have inherited a secure lock icon from an HTTPS page. This vulnerability affects Firefox ESR < 78.10, Thunderbird < 78.10, and Firefox < 88.

When was CVE-2021-23998 disclosed?

CVE-2021-23998 was first published in the National Vulnerability Database on June 24, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-23998 actively exploited?

CVE-2021-23998 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 37.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-23998?

CVE-2021-23998 has a CVSS v3 base score of 6.5 (NVD).

How do I remediate CVE-2021-23998?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-23998, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-23998

Explore →

Is Your Infrastructure Affected by CVE-2021-23998?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs

CVE-2021-23998

Published

Last Modified

References (8)

Patch Availability(11)

Weakness Classification(1)

Data Freshness Timeline

Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-23998?

Same vendor

Same CWE

CVE-2021-23998

📅 Published

🔄 Last Modified

🔗 References (8)

Patch Availability(11)

Weakness Classification(1)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-23998?

🔗 Related CVEs(same vendor + same CWE)

Same vendor

Same CWE

Published

Last Modified

References (8)

Frequently asked(5)

Related CVEs(same vendor + same CWE)