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Public proof of conceptFix available

CVE-2021-42697

A public proof of concept exists; no exploitation attested.

  • Published2021-11-02
  • Fixed in10.2.7 · 10.1.15
  • WeaknessCWE-674

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Akka HTTP 10.1.x before 10.1.15 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.

Timeline

dates in UTC
  1. 2021-11-0222:15CVE publishedNVD
  2. 2022-05-11Exploit-DB entryExploit-DB

Observed activity

isMalicious corpus · updated 2026-11-03 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-42697?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-42697?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD · OSV
Akka http server
BranchAffectedFixed in
10.2≥ 10.2.0, < 10.2.710.2.7
10.2≥ 10.2.0-M1, < 10.2.710.2.7
10.1≥ 10.1.0, < 10.1.1510.1.15
aakka-http-core_2.13.0-M3
BranchAffectedFixed in
10.1+≥ 10.1.0no fix published
akka-http-core_2.13.0-M5
BranchAffectedFixed in
10.1+≥ 10.1.0no fix published

2 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Akka http server to 10.2.7 · 10.1.15

Advisories and patches

Detection

read 2026-11-03 22:42 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
EDB-50892
Exploit-DB
Proof-of-concept repositories
1 repository, unverifiedcxosmo/CVE-2021-42697
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Published
2021-11-02
Last Modified
2026-06-17
NVD status
Modified
GitHub Advisory
GHSA-3hw2-h67c-wq66

Frequently asked questions

What is CVE-2021-42697?

Akka HTTP 10.1.x before 10.1.15 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.

Is CVE-2021-42697 actively exploited?

Active exploitation of CVE-2021-42697 has not been confirmed. Its EPSS score was 36.1% on 2026-11-03, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-42697?

CVE-2021-42697 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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Sources for this record