VulnerabilityPublished 26 Feb 2026

CVE-2026-27829: withastro astro · Server-Side Request Forgery (SSRF)

Affects withastro astroSource CVE Database V5

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Not known to be exploited · CVSS 6.5 Medium : upgrade to 9.5.4 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 24% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 9.5.4

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
Availability: Low

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

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, 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: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
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 on the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 26 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 30 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 withastro astro to 9.5.4.

Affected software

Product	Affected	Fixed in
withastroastro	Affected >=9.0.0 <9.5.4	Fixed in 9.5.4

AI-suggested

Upgrade all Astro framework instances to version 9.5.4 or later, where the SSRF vulnerability is fixed by enforcing domain validation during `inferSize` image fetches. Until upgrading, as a temporary mitigation, disable the `inferSize` option if it is not essential, preventing automatic remote image fetching. Additionally, implement strict input validation and sanitization on any user-controllable image URLs to prevent injection of arbitrary hosts. Employ network-level controls such as egress filtering and firewall rules to restrict server outbound HTTP requests to only trusted domains and IP ranges. Monitor application logs for unusual outbound requests to internal or unexpected external hosts. Conduct security reviews of CMS or user input mechanisms that influence image URLs to reduce attack surface. Finally, maintain up-to-date threat intelligence and patch management processes to respond promptly to similar vulnerabilities.

Description

Astro is a web framework. In versions 9.0.0 through 9.5.3, a bug in Astro's image pipeline allows bypassing `image.domains` / `image.remotePatterns` restrictions, enabling the server to fetch content from unauthorized remote hosts. Astro provides an `inferSize` option that fetches remote images at render time to determine their dimensions. Remote image fetches are intended to be restricted to domains the site developer has manually authorized (using the `image.domains` or `image.remotePatterns` options). However, when `inferSize` is used, no domain validation is performed — the image is fetched from any host regardless of the configured restrictions. An attacker who can influence the image URL (e.g., via CMS content or user-supplied data) can cause the server to fetch from arbitrary hosts. This allows bypassing `image.domains` / `image.remotePatterns` restrictions to make server-side requests to unauthorized hosts. This includes the risk of server-side request forgery (SSRF) against internal network services and cloud metadata endpoints. Version 9.5.4 fixes the issue.

Impact

Organizations using vulnerable versions of the Astro framework (9.0.0 to 9.5.3) risk unauthorized internal network access via SSRF attacks. This can lead to exposure of sensitive internal services, cloud metadata endpoints (potentially leaking cloud credentials), and other protected resources. The SSRF can be leveraged to pivot attacks within the internal network, escalate privileges, or exfiltrate data. Since the vulnerability requires no authentication or user interaction, it can be exploited remotely by unauthenticated attackers if they can influence image URLs. This poses a significant risk to web applications relying on Astro for image processing, especially those integrated with internal APIs, cloud infrastructure, or sensitive backend services. The medium severity score reflects the moderate impact on integrity and availability, with no direct confidentiality impact unless combined with further exploitation. However, the potential for chained attacks increases the overall threat.

CWE-918Server-Side Request Forgery (opens in a new tab)
Base weaknessCWE Top 25 (2025): #22OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
Implementation · Operation
If there is a known list of applications, IP, hostname, and/or domains to which the product is allowed to communicate, then use allowlists to ensure that outgoing requests are restricted to these known entities. The allowlists could be in the application code or possibly enforced by firewalls or network segmentation.
Implementation · Operation
If the product is expected to be able to connect to arbitrary IP addresses or domains, consider using a denylist that includes private network addresses, internal domain names, etc. The denylist could be in the application code or possibly enforced by firewalls or network segmentation.
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.
OWASP Cheat Sheets
Server Side Request Forgery Prevention (opens in a new tab)
Unvalidated Redirects and Forwards (opens in a new tab)
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.6.1 (opens in a new tab)
V5.2.6 (opens in a new tab)
Attack patterns
Server Side Request Forgery (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, 11:14 UTC

WeaknessesCWE-918

Technical details

References

Community reviews

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