Astro: Remote allowlist bypass via unanchored matchPathname wildcard

published 2026-03-24 7 mo ago modified 2026-06-17 4 mo ago also GHSA-g735-7g2w-hh3f , EUVD-2026-14984

cvss: 5.3; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits: 0; none known

Astro is a web framework. From version 2.10.10 to before version 5.18.1, this issue concerns Astro's remotePatterns path enforcement for remote URLs used by server-side fetchers such as the image optimization endpoint. The path matching logic for /* wildcards is unanchored, so a pathname that contains the allowed prefix later in the path can still match. As a result, an attacker can fetch paths outside the intended allowlisted prefix on an otherwise allowed host. This issue has been patched in version 5.18.1.

Patch / fix

fixed in 2

npm astro 5.18.1
astro astro 5.18.1

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 7 mo ago (2026-03-24)

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/withastro/astro/security/advisories/GHSA-g735-7g2w-hh3f referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	2.9	CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P
CNA	4.0	2.9	CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
GitHub	3.1	5.3	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Affected packages

ecosystem	package	affected	fixed in
npm	astro	>=2.10.10, <5.18.1	5.18.1

Affected products

withastro astro

Classification

Weakness

CWE-20 Improper Input Validation
CWE-183 Permissive List of Allowed Inputs

References

github.com /withastro/astro/security/advisories/GHSA-g735-7g2w-hh3f
web, exploit, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2026-33769
advisory
github.com /withastro/astro
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary