CVE-2021-38997Network attack vector

Session hijacking via improper Host validation

Published Dec 1, 2022 · Updated Apr 23, 2025

HTTP header injection in IBM API Connect V10 and V2018 management servers allows remote authenticated users to manipulate HTTP handling. The management server improperly validates attacker-controlled Host header values; IBM has not published the affected endpoint or the precise operation that propagates them. Low-privileged access is required, and successful exploitation enables cross-site scripting, cache poisoning, or session hijacking.

CVSS severity5.4
Medium
EPSS probability0.39%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTTP header injection in IBM API Connect V10 and V2018 management servers allows remote authenticated users to manipulate HTTP handling. The management server improperly validates attacker-controlled Host header values; IBM has not published the affected endpoint or the precise operation that propagates them. Low-privileged access is required, and successful exploitation enables cross-site scripting, cache poisoning, or session hijacking.

The record

CVE
CVE-2021-38997
Published
Dec 1, 2022
Updated
Apr 23, 2025
Vendor
IBM
Product
API Connect
Classifications
CWE-644, CWE-116
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Dec 1, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=10.0.0.0 <10.0.5.0
  2. Affected versionversion=10.0.1.0 <10.0.1.7
  3. Affected versionversion=2018.4.1.0 <2018.4.1.19

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

IBM · API Connectversion=10.0.0.0 <10.0.5.0; version=10.0.1.0 <10.0.1.7; version=2018.4.1.0 <2018.4.1.19

Published CVSS scores

5.4IBM CorporationCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-644Improper Neutralization of HTTP Headers for Scripting Syntax
CWE-116Improper Encoding or Escaping of Output

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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