EUVD-2026-49586
GHSA-r557-wffq-wvrc
Severity by source
CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:N/SI:L/SA:N/E:X/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
Primary rating from Vendor (https://github.com/withastro/astro) · only source for this CVE.
CVSS VectorVendor: https://github.com/withastro/astro
Lifecycle Timeline
2Blast Radius
ecosystem impact- 3 npm packages depend on @astrojs/node (2 direct, 1 indirect)
Ecosystem-wide dependent count for version 8.1.0.
DescriptionCVE.org
Impact
With trailingSlash: 'always' configured, the @astrojs/node standalone server's static file handler appends a trailing slash to request paths and issues a 301 redirect. Paths beginning with /\ (slash-backslash) were not recognized as internal paths, so the handler would echo the raw path back in the Location header. Because browsers treat \ as / per the WHATWG URL specification, the resulting redirect could resolve to an external host.
Preconditions:
trailingSlash: 'always'must be set (non-default; the default is'ignore')- The request path must not have a file extension in its final segment
- An attacker must deliver the crafted link to a user
Patches
Fixed by treating backslash-prefixed paths the same as //-prefixed paths in isInternalPath(), so they are no longer rewritten with a trailing slash.
Workarounds
Use the default trailingSlash: 'ignore' setting, which does not issue trailing-slash redirects in the static file handler.
References
AnalysisAI
Open redirect in the @astrojs/node standalone server's static file handler allows remote attackers to redirect authenticated or unauthenticated users to arbitrary external hosts via crafted slash-backslash paths. Versions 8.1.0 through 11.0.1 of the npm package fail to normalize backslash characters before the internal-path prefix check in isInternalPath(), causing the 301 Location header to echo back paths like /\attacker.com/page which browsers resolve as //attacker.com/page per the WHATWG URL specification. No public exploit is identified at time of analysis; exploitation is gated by a non-default configuration option and requires social engineering to deliver a crafted link to a victim.
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External POC / Exploit Code
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