CVE-2021-23408Public exploitNetwork attack vector

Client-side object pollution via recursive URL merge

Published Jul 21, 2021 · Updated Sep 16, 2024

Prototype pollution in GraphHopper web bundle before 3.2 and 4.0 prereleases allows remote attackers to alter client-side object behavior. The mergeParamIntoObject function recursively follows dot-separated URL keys without rejecting proto, constructor, or prototype segments. Exploitation requires a victim to open a crafted GraphHopper Maps URL; the polluted prototype can change or interrupt behavior in that browser session.

CVSS severity5.4
Medium
EPSS probability1.40%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Prototype pollution in GraphHopper web bundle before 3.2 and 4.0 prereleases allows remote attackers to alter client-side object behavior. The mergeParamIntoObject function recursively follows dot-separated URL keys without rejecting proto, constructor, or prototype segments. Exploitation requires a victim to open a crafted GraphHopper Maps URL; the polluted prototype can change or interrupt behavior in that browser session.

The record

CVE
CVE-2021-23408
Published
Jul 21, 2021
Updated
Sep 16, 2024
Vendor
GraphHopper
Product
GraphHopper
Classifications
CWE-1321, CAPEC-1, CAPEC-180, CAPEC-77, T1204.001
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 21, 2021CVE publishedPublication date reported by the CVE source.
  2. Sep 16, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

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

  1. Affected versionversion=4.0-pre1 <unspecified
  2. Affected versionversion=unspecified <3.2
  3. Affected versionversion=unspecified <4.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

GraphHopper · GraphHopperversion=4.0-pre1 <unspecified; version=unspecified <3.2; version=unspecified <4.0

Published CVSS scores

5.4SnykCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:L
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N
4.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/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
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-1321Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
CAPEC-1Accessing Functionality Not Properly Constrained by ACLs
CAPEC-180Exploiting Incorrectly Configured Access Control Security Levels
CAPEC-77Manipulating User-Controlled Variables
T1204.001User Execution: Malicious Link

Public exploit references

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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