CVE-2021-25761

MEDIUMNVD 5.35.3—

5.3

In JetBrains Ktor before 1.5.0, a birthday attack on SessionStorage key was possible.

CVSS v3: 5.3
EG Score: 5.3(medium)
EPSS: 0.0%
KEV: Not listed

Published

February 3, 2021

Last Modified

November 21, 2024

References (4)

cve@mitrehttps://blog.jetbrains.com
cve@mitrehttps://blog.jetbrains.com/blog/2021/02/03/jetbrains-security-bulletin-q4-2020/
af854a3a-2127-422b-91ae-364da2661108https://blog.jetbrains.com
af854a3a-2127-422b-91ae-364da2661108https://blog.jetbrains.com/blog/2021/02/03/jetbrains-security-bulletin-q4-2020/

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 6× in last 7d / 10× 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.

2026-06-01 13:50 UTCepss_batch
2026-06-01 13:50 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
2026-05-27 13:39 UTCepss_batch
2026-05-26 21:23 UTCEG score recompute
2026-05-26 21:23 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2021-25761?

CVE-2021-25761 is a medium vulnerability published on February 3, 2021. In JetBrains Ktor before 1.5.0, a birthday attack on SessionStorage key was possible.

When was CVE-2021-25761 disclosed?

CVE-2021-25761 was first published in the National Vulnerability Database on February 3, 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-2021-25761 actively exploited?

CVE-2021-25761 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-25761?

CVE-2021-25761 has a CVSS v3 base score of 5.3 (NVD).

How do I remediate CVE-2021-25761?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-25761, 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-2021-25761

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CVE-2021-25761

📅 Published

🔄 Last Modified

🔗 References (4)

Weakness Classification(2)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-25761?

🔗 Related CVEs(same CWE)

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Published

Last Modified

References (4)

Frequently asked(5)

Related CVEs(same CWE)