CVE-2026-34931Public exploitNetwork attack vector

Account takeover via prefix-only redirect validation

Published Apr 2, 2026 · Updated Apr 2, 2026

Open redirect in Hoppscotch self-hosted backend before 2026.3.0 allows remote attackers to steal session tokens through device login. The device-login handler validates redirect_uri with a prefix-only http://localhost string check, so attacker-controlled hosts such as localhost.evil.com pass. A victim must open the crafted URL and click Proceed; the resulting access and refresh tokens let the attacker sign in as that victim.

CVSS severity8.5
High
EPSS probability0.37%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Open redirect in Hoppscotch self-hosted backend before 2026.3.0 allows remote attackers to steal session tokens through device login. The device-login handler validates redirect_uri with a prefix-only http://localhost string check, so attacker-controlled hosts such as localhost.evil.com pass. A victim must open the crafted URL and click Proceed; the resulting access and refresh tokens let the attacker sign in as that victim.

The record

CVE
CVE-2026-34931
Published
Apr 2, 2026
Updated
Apr 2, 2026
Vendor
Hoppscotch
Product
Hoppscotch
Classifications
CWE-601, T1528
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 2, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 2, 2026Record 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=< 2026.3.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Hoppscotch · Hoppscotchversion=< 2026.3.0

Published CVSS scores

9.6NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
8.5GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA: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-601URL Redirection to Untrusted Site ('Open Redirect')
T1528Steal Application Access Token

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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