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Uncontrolled Recursion in Akka HTTP

High severity GitHub Reviewed Published May 24, 2022 to the GitHub Advisory Database • Updated Sep 30, 2025

Package

maven com.typesafe.akka:aakka-http-core_2.13.0-M3 (Maven)

Affected versions

>= 10.1.0, < 10.1.15

Patched versions

None
maven com.typesafe.akka:akka-http-core_2.11 (Maven)
>= 10.1.0, < 10.1.15
10.1.15
maven com.typesafe.akka:akka-http-core_2.12 (Maven)
>= 10.1.0, < 10.1.15
>= 10.2.0-M1, < 10.2.7
10.1.15
10.2.7
maven com.typesafe.akka:akka-http-core_2.13 (Maven)
>= 10.1.0, < 10.1.15
>= 10.2.0-M1, < 10.2.7
10.1.15
10.2.7
maven com.typesafe.akka:akka-http-core_2.13.0-M5 (Maven)
>= 10.1.0, < 10.1.15
None
maven com.typesafe.akka:akka-http-core_2.13.0-RC2 (Maven)
>= 10.1.0, < 10.1.15
None
maven com.typesafe.akka:akka-http-core_2.13.0-RC3 (Maven)
>= 10.1.0, < 10.1.15
None

Description

Akka HTTP 10.1.x and 10.2.x before 10.2.7 can encounter stack exhaustion while parsing HTTP headers, which allows a remote attacker to conduct a Denial of Service attack by sending a User-Agent header with deeply nested comments.

References

Published by the National Vulnerability Database Nov 2, 2021
Published to the GitHub Advisory Database May 24, 2022
Reviewed Jun 21, 2022
Last updated Sep 30, 2025

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(99th percentile)

Weaknesses

Uncontrolled Recursion

The product does not properly control the amount of recursion that takes place, consuming excessive resources, such as allocated memory or the program stack. Learn more on MITRE.

Out-of-bounds Write

The product writes data past the end, or before the beginning, of the intended buffer. Learn more on MITRE.

CVE ID

CVE-2021-42697

GHSA ID

GHSA-3hw2-h67c-wq66

Source code

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