Security readout for executives and security teams
Plain-English summary
Astro versions 9.0.0 through 9.5.3 can fetch remote images from hosts that site owners did not approve when the inferSize option is used. If attackers can control an image URL through CMS or user content, the server may make unintended requests, including toward internal services.
Executive priority
Treat as a timely upgrade for affected Astro sites, especially public sites with CMS or user-supplied image content. The main business concern is unintended server-side access to internal or cloud resources, not direct remote code execution.
Technical view
The vulnerability is an SSRF-related bypass in Astro’s remote image sizing path. image.domains and image.remotePatterns are not enforced when inferSize fetches a remote image at render time. The issue is tracked as CWE-918 and fixed in Astro 9.5.4. CVSS is 6.5, medium severity.
Likely exposure
Exposure is most likely for Astro applications on versions >=9.0.0 and <9.5.4 that use inferSize with remote image URLs influenced by CMS entries, user input, or other untrusted data.
Exploitation context
No active exploitation is stated in the provided sources, and the CVE is not marked KEV. Abuse requires the application to process attacker-influenced remote image URLs through inferSize, causing server-side outbound requests to unauthorized hosts.
Researcher notes
The key condition is missing allowlist enforcement in the inferSize remote fetch path. Validate exposure by confirming affected Astro versions and attacker influence over remote image URLs. Avoid assuming impact where inferSize is unused or URLs are fully trusted.
Mitigation direction
- Upgrade Astro to version 9.5.4 or later.
- Review use of inferSize with remote images.
- Restrict who can supply or edit remote image URLs.
- Follow Astro’s advisory for any additional vendor guidance.
- Monitor outbound server requests for unexpected destinations.
Validation and detection
- Inventory Astro applications and package versions.
- Confirm whether versions are >=9.0.0 and <9.5.4.
- Search code and templates for inferSize usage.
- Review CMS or user-controlled fields used as image URLs.
- Verify production dependencies were rebuilt after upgrading.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-918: Information exposure and cloud metadata lookup
Information exposure and SSRF weaknesses can make discovery, cloud metadata, and credential material review relevant. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCloud metadata behavior lookup
The CVE wording references SSRF or metadata access, so cloud discovery and credential material review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-27829 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L3.92.5Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/withastro/astro/security/advisories/GHSA-cj9f-h6r6-4cx2CVE reference · x_refsource_CONFIRM
- https://github.com/withastro/astro/commit/e01e98b063e90d274c42130ec2a60cc0966622c9CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Server-Side Request Forgery (SSRF)
Server-Side Request Forgery (SSRF) represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.