VulnerabilityPublished 25 Feb 2026Updated 27 Feb 2026

CVE-2026-27738: angular-cli · Open Redirect

Affects angular-cliSource CVE Database V5

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Not known to be exploited · CVSS 6.9 Medium · fixed in 21.2.0-rc.0 : update angular-cli when convenient.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score

6.9Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.3% chance of exploitation in 30 days – higher than 28% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 21.2.0-rc.0, 21.1.5, 20.3.17 +1

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

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: Low
Subsequent system integrity: Low
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, up to and including the entire Internet. Such a vulnerability is often termed “remotely exploitable” and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Subsequent System.
Subsequent system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade angular-cli to 21.2.0-rc.0, 21.1.5, 20.3.17 or 19.2.21; angular-cli to 20.3.17 or 19.2.21.

Affected software

Product	Affected	Fixed in
angularangular-cli	Affected >=21.2.0-next.2 <21.2.0-rc.0	Fixed in 21.2.0-rc.0
angularangular-cli	Affected >=21.0.0-next.0 <21.1.5	Fixed in 21.1.5
angularangular-cli	Affected >=20.0.0-next.0 <20.3.17	Fixed in 20.3.17
angularangular-cli	Affected >=19.0.0-next.0 <19.2.21	Fixed in 19.2.21
npmangular-cli`pkg:npm/angular-cli`Other threats	Affected <19.2.21 >=20.0.0 <20.3.17	Fixed in 19.2.21 20.3.17

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Upgrade angular-cli to the patched versions: 19.2.21 or later, 20.3.17 or later, and 21.1.5 or later (including 21.2.0-rc.1).
If you cannot patch yet, implement manual sanitization of the X-Forwarded-Prefix header in the server.ts file to strip or validate multiple leading slashes and reject suspicious header values before Angular SSR processes the request.
Configure reverse proxies and CDNs to either not forward the X-Forwarded-Prefix header or sanitize it to prevent multiple leading slashes.
Adjust caching policies to vary cache entries based on the X-Forwarded-Prefix header to avoid serving cached malicious redirects.
Audit application routes that perform internal redirects to ensure they validate and constrain redirect targets strictly to trusted internal URLs.
Monitor web traffic and logs for unusual redirect patterns or requests containing suspicious X-Forwarded-Prefix header values.
Educate developers and DevOps teams about this vulnerability and the importance of secure header handling in SSR environments.
Employ web application firewalls (WAFs) with rules to detect and block open redirect attempts involving malformed X-Forwarded-Prefix headers.

Description

The Angular SSR is a server-rise rendering tool for Angular applications. An Open Redirect vulnerability exists in the internal URL processing logic in versions on the 19.x branch prior to 19.2.21, the 20.x branch prior to 20.3.17, and the 21.x branch prior to 21.1.5 and 21.2.0-rc.1. The logic normalizes URL segments by stripping leading slashes; however, it only removes a single leading slash. When an Angular SSR application is deployed behind a proxy that passes the `X-Forwarded-Prefix` header, an attacker can provide a value starting with three slashes. This vulnerability allows attackers to conduct large-scale phishing and SEO hijacking. In order to be vulnerable, the application must use Angular SSR, the application must have routes that perform internal redirects, the infrastructure (Reverse Proxy/CDN) must pass the `X-Forwarded-Prefix` header to the SSR process without sanitization, and the cache must not vary on the `X-Forwarded-Prefix` header. Versions 21.2.0-rc.1, 21.1.5, 20.3.17, and 19.2.21 contain a patch. If you cannot patch yet, developers should sanitize the `X-Forwarded-Prefix` header in their`server.ts` before the Angular engine processes the request.

Impact

This vulnerability allows attackers to redirect users of vulnerable Angular SSR applications to malicious external websites without their consent or knowledge. The primary risks include large-scale phishing attacks, where users may be tricked into divulging sensitive information such as credentials or financial data, and SEO hijacking, which can damage the reputation and search engine rankings of legitimate sites. Organizations running Angular SSR behind proxies or CDNs that forward the X-Forwarded-Prefix header without proper sanitization are at risk. The impact extends to confidentiality (through phishing), integrity (by misleading users and search engines), and availability (potentially through user trust erosion). Because exploitation requires no authentication or user interaction and can be performed remotely, the threat can be widespread and automated. However, the scope is limited to Angular SSR applications with specific infrastructure configurations, reducing the overall attack surface. Nevertheless, organizations relying on Angular SSR for critical web applications, especially those with high user traffic or sensitive data, face significant reputational and operational risks if unpatched.

CWE-601URL Redirection to Untrusted Site (Open Redirect) (opens in a new tab)
Base weaknessLikelihood of exploit: LowOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a redirect.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
Architecture and Design
Use an intermediate disclaimer page that provides the user with a clear warning that they are leaving the current site. Implement a long timeout before the redirect occurs, or force the user to click on the link. Be careful to avoid XSS problems (CWE-79) when generating the disclaimer page.
Architecture and Design · Enforcement by Conversion
When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
OWASP Cheat Sheets
Mass Assignment (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V5.1.5 (opens in a new tab)
Attack patterns
Cross-Site Flashing (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Mar 2026, 09:49 UTC

WeaknessesCWE-601

Technical details

References

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