CVE-2026-33397Network attack vector

Open redirect via backslash prefix validation bypass

Published Mar 26, 2026 · Updated Mar 26, 2026

Open redirect in Angular SSR before 20.3.21, 21.2.3, or 22.0.0-next.2 allows remote attackers to redirect users via a proxy header. The INVALID_PREFIX_REGEX in packages/angular/ssr/src/utils/validation.ts accepts a leading backslash in X-Forwarded-Prefix, after which redirect construction prepends a slash and browsers interpret the result as a protocol-relative URL. Exploitation requires a proxy to pass the header; absent Vary: X-Forwarded-Prefix, a shared cache can serve the poisoned redirect to later users.

CVSS severity6.9
Medium
EPSS probability0.26%
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 Angular SSR before 20.3.21, 21.2.3, or 22.0.0-next.2 allows remote attackers to redirect users via a proxy header. The INVALID_PREFIX_REGEX in packages/angular/ssr/src/utils/validation.ts accepts a leading backslash in X-Forwarded-Prefix, after which redirect construction prepends a slash and browsers interpret the result as a protocol-relative URL. Exploitation requires a proxy to pass the header; absent Vary: X-Forwarded-Prefix, a shared cache can serve the poisoned redirect to later users.

The record

CVE
CVE-2026-33397
Published
Mar 26, 2026
Updated
Mar 26, 2026
Vendor
Angular
Product
Angular CLI
Classifications
CWE-601
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 26, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 26, 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=>= 20.0.0-next.0, < 20.3.21
  2. Affected versionversion=>= 21.0.0-next.0, < 21.2.3
  3. Affected versionversion=>= 22.0.0-next.0, < 22.0.0-next.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Angular · Angular CLIversion=>= 20.0.0-next.0, < 20.3.21; version=>= 21.0.0-next.0, < 21.2.3; version=>= 22.0.0-next.0, < 22.0.0-next.2

Published CVSS scores

6.1NIST National Vulnerability DatabaseCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
6.9GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/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 exploitUnconfirmed

Weakness, pattern, technique

CWE-601URL Redirection to Untrusted Site ('Open Redirect')

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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