How severe is CVE-2021-23339?

CVE-2021-23339 has a CVSS 3.x base score of 5.0, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability low.

Is CVE-2021-23339 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-23339?

CVE-2021-23339 affects Lightbend Akka-http. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-23339?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-23339 published?

CVE-2021-23339 was published on 2021-02-17 and last updated on 2026-06-17.

CVE-2021-23339

CVE-2021-23339 is a medium-severity vulnerability in Lightbend Akka-http with a CVSS 3.x base score of 5.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-444.

Key facts

Severity: Medium (CVSS 3.x base score 5.0)
CVSS v2: 6.4
EPSS exploit prediction: 1% (49th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-444
Affected product: Lightbend Akka-http
Published: 2021-02-17
Last modified: 2026-06-17

Description

This affects all versions before 10.1.14 and from 10.2.0 to 10.2.4 of package com.typesafe.akka:akka-http-core. It allows multiple Transfer-Encoding headers.

Frequently asked questions

What is CVE-2021-23339?: This affects all versions before 10.1.14 and from 10.2.0 to 10.2.4 of package com.typesafe.akka:akka-http-core. It allows multiple Transfer-Encoding headers.
How severe is CVE-2021-23339?: CVE-2021-23339 has a CVSS 3.x base score of 5.0, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability low.
Is CVE-2021-23339 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (49th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-23339?: CVE-2021-23339 affects Lightbend Akka-http. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-23339?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-23339 published?: CVE-2021-23339 was published on 2021-02-17 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:lightbend:akka-http:*:*:*:*:*:*:*:*

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