Fast Uri
Monthly
Parsing and serialization inconsistency in fast-uri, the Node.js URI parser core to the Fastify ecosystem, allows network-accessible, unauthenticated attackers to supply percent-encoded slashes in the scheme component, causing the library to report host as undefined during parsing while serialization emits a network-path reference with an attacker-controlled authority. Applications that allowlist requests on the parsed host value, or that treat a no-authority parse result as safe to resolve against a base URI, are bypassed - enabling server-side request forgery, off-site redirects, and address-policy evasion. No public exploit has been identified at time of analysis, but the CVSS vector (AV:N/AC:L/PR:N/UI:N) confirms exploitation requires no authentication and no special configuration, making affected deployments an immediate upgrade priority.
Double-decoding of percent-encoded hostnames in fast-uri (Node.js URI parser) creates a server-side request forgery and host-policy bypass primitive in versions 2.4.1-2.4.4, 3.1.2-3.1.5, and 4.0.0-4.1.2. The library decodes percent escapes once during hostname parsing and again during authority recomposition, so a single normalize or resolve call on a doubly-encoded input can silently resolve to a different network destination - including loopback addresses - than the encoded form represents. Any application layer sitting fast-uri in front of outbound routing guards, redirect allow-lists, or host-policy checks is therefore vulnerable to SSRF. This is an incomplete-fix variant of CVE-2026-6322; no public exploit code or active exploitation (CISA KEV) has been identified at time of analysis.
Host confusion in fast-uri, a Node.js URI parser in the Fastify ecosystem, allows policy bypass by exploiting inconsistent host canonicalization between the library's own entry points. When a scheme-relative reference (e.g., //unicode-host.example/path) is passed without an explicit scheme, fast-uri's parse, normalize, and equal functions return the host verbatim, while resolve canonicalizes it to ASCII/Punycode - meaning the same input yields different host values depending on which API is called. An application that extracts a host for an allowlist check via one code path and then resolves the URI via another can be tricked into approving one host while the actual request is dispatched to a different one. No public exploit exists and CISA KEV listing is absent, but the EPSS-independent integrity impact (CVSS I:H) is real in applications relying on fast-uri for security-critical URI validation. Fixed versions are 2.4.5, 3.1.6, and 4.1.3.
Security filter bypass in fast-uri (before versions 4.1.2, 3.1.5, and 2.4.4) enables unauthenticated remote attackers to circumvent host-based access controls - including SSRF filters, allowlists, and redirect validators - by submitting URLs that use backslash-based authority introducers. The parser inconsistency between fast-uri and Node.js's native WHATWG URL handler causes the same crafted URL to resolve to different hosts in each parser, allowing attackers to steer downstream requests to unintended destinations. No public exploit is identified at time of analysis and this CVE does not appear in CISA KEV, though the CVSS 7.5 High rating with AV:N/AC:L/PR:N/UI:N reflects straightforward remote exploitability wherever the vulnerable application pattern exists.
Host-based policy bypass in the fast-uri Node.js URI parser (versions 2.3.1 through 4.1.0, spanning the 2.x line up to 2.4.2 and the 3.x line up to 3.1.3) allows remote attackers to smuggle a different host past allowlist, denylist, SSRF, loopback, and redirect-validation checks by using a literal backslash. Because fast-uri does not treat U+005C as an authority delimiter while Node's native WHATWG URL parser (used by fetch, undici, and the http/https clients) normalizes backslash to forward slash for special schemes, the two parsers disagree on the host, enabling requests to be steered to cloud metadata, loopback, or internal endpoints. There is no public exploit identified at time of analysis, but the flaw is trivially triggerable in affected deployments and openjsf has published a fix.
Host-based security policy bypass in the fast-uri Node.js URI parser (versions 2.3.1 through 3.1.2 and 4.0.0) lets remote attackers defeat denylists, loopback filters, redirect validation, and SSRF/proxy-routing controls by supplying Unicode (IDN) hostnames. Because fast-uri's IDN path invokes a non-existent helper on the global URL constructor, it leaves the host in raw Unicode form while normalize() and equal() report a host that differs from what Node's WHATWG URL or fetch ultimately resolve, producing a parser-differential bypass. No public exploit is identified at time of analysis, but the bypass is trivially reproducible and primarily enables SSRF-style integrity attacks.
Authority confusion in fast-uri JavaScript library allows remote attackers to bypass URL validation security controls. The normalize() function improperly decodes percent-encoded at-signs (%40) in hostnames, then re-serializes them as raw userinfo delimiters, causing URLs like 'http://trusted.com%40evil.com' to resolve to 'evil.com' instead of 'trusted.com'. Applications using fast-uri to validate URLs against allowlists or for redirect validation can be tricked into connecting to attacker-controlled domains. CVSS 7.5 (AV:N/AC:L/PR:N/UI:N) indicates trivial remote exploitation with no authentication. EPSS data not available; no confirmed active exploitation (not in CISA KEV). Vendor patch released in version 3.1.2.
Path normalization bypass in fast-uri 3.1.0 and earlier allows remote attackers to circumvent path-based access controls through percent-encoded path traversal sequences. The normalize() and equal() functions decode URL-encoded separators (%2F) and dot segments (%2E) before applying normalization rules, causing distinct URIs to collapse onto identical normalized paths. Applications relying on fast-uri for URL validation in authorization checks can be tricked into allowing access to restricted resources. EPSS exploitation probability not yet calculated given recent disclosure; no active exploitation confirmed (not in CISA KEV), but attack vector is trivial (CVSS AV:N/AC:L/PR:N/UI:N) and patch is available in version 3.1.1.
Parsing and serialization inconsistency in fast-uri, the Node.js URI parser core to the Fastify ecosystem, allows network-accessible, unauthenticated attackers to supply percent-encoded slashes in the scheme component, causing the library to report host as undefined during parsing while serialization emits a network-path reference with an attacker-controlled authority. Applications that allowlist requests on the parsed host value, or that treat a no-authority parse result as safe to resolve against a base URI, are bypassed - enabling server-side request forgery, off-site redirects, and address-policy evasion. No public exploit has been identified at time of analysis, but the CVSS vector (AV:N/AC:L/PR:N/UI:N) confirms exploitation requires no authentication and no special configuration, making affected deployments an immediate upgrade priority.
Double-decoding of percent-encoded hostnames in fast-uri (Node.js URI parser) creates a server-side request forgery and host-policy bypass primitive in versions 2.4.1-2.4.4, 3.1.2-3.1.5, and 4.0.0-4.1.2. The library decodes percent escapes once during hostname parsing and again during authority recomposition, so a single normalize or resolve call on a doubly-encoded input can silently resolve to a different network destination - including loopback addresses - than the encoded form represents. Any application layer sitting fast-uri in front of outbound routing guards, redirect allow-lists, or host-policy checks is therefore vulnerable to SSRF. This is an incomplete-fix variant of CVE-2026-6322; no public exploit code or active exploitation (CISA KEV) has been identified at time of analysis.
Host confusion in fast-uri, a Node.js URI parser in the Fastify ecosystem, allows policy bypass by exploiting inconsistent host canonicalization between the library's own entry points. When a scheme-relative reference (e.g., //unicode-host.example/path) is passed without an explicit scheme, fast-uri's parse, normalize, and equal functions return the host verbatim, while resolve canonicalizes it to ASCII/Punycode - meaning the same input yields different host values depending on which API is called. An application that extracts a host for an allowlist check via one code path and then resolves the URI via another can be tricked into approving one host while the actual request is dispatched to a different one. No public exploit exists and CISA KEV listing is absent, but the EPSS-independent integrity impact (CVSS I:H) is real in applications relying on fast-uri for security-critical URI validation. Fixed versions are 2.4.5, 3.1.6, and 4.1.3.
Security filter bypass in fast-uri (before versions 4.1.2, 3.1.5, and 2.4.4) enables unauthenticated remote attackers to circumvent host-based access controls - including SSRF filters, allowlists, and redirect validators - by submitting URLs that use backslash-based authority introducers. The parser inconsistency between fast-uri and Node.js's native WHATWG URL handler causes the same crafted URL to resolve to different hosts in each parser, allowing attackers to steer downstream requests to unintended destinations. No public exploit is identified at time of analysis and this CVE does not appear in CISA KEV, though the CVSS 7.5 High rating with AV:N/AC:L/PR:N/UI:N reflects straightforward remote exploitability wherever the vulnerable application pattern exists.
Host-based policy bypass in the fast-uri Node.js URI parser (versions 2.3.1 through 4.1.0, spanning the 2.x line up to 2.4.2 and the 3.x line up to 3.1.3) allows remote attackers to smuggle a different host past allowlist, denylist, SSRF, loopback, and redirect-validation checks by using a literal backslash. Because fast-uri does not treat U+005C as an authority delimiter while Node's native WHATWG URL parser (used by fetch, undici, and the http/https clients) normalizes backslash to forward slash for special schemes, the two parsers disagree on the host, enabling requests to be steered to cloud metadata, loopback, or internal endpoints. There is no public exploit identified at time of analysis, but the flaw is trivially triggerable in affected deployments and openjsf has published a fix.
Host-based security policy bypass in the fast-uri Node.js URI parser (versions 2.3.1 through 3.1.2 and 4.0.0) lets remote attackers defeat denylists, loopback filters, redirect validation, and SSRF/proxy-routing controls by supplying Unicode (IDN) hostnames. Because fast-uri's IDN path invokes a non-existent helper on the global URL constructor, it leaves the host in raw Unicode form while normalize() and equal() report a host that differs from what Node's WHATWG URL or fetch ultimately resolve, producing a parser-differential bypass. No public exploit is identified at time of analysis, but the bypass is trivially reproducible and primarily enables SSRF-style integrity attacks.
Authority confusion in fast-uri JavaScript library allows remote attackers to bypass URL validation security controls. The normalize() function improperly decodes percent-encoded at-signs (%40) in hostnames, then re-serializes them as raw userinfo delimiters, causing URLs like 'http://trusted.com%40evil.com' to resolve to 'evil.com' instead of 'trusted.com'. Applications using fast-uri to validate URLs against allowlists or for redirect validation can be tricked into connecting to attacker-controlled domains. CVSS 7.5 (AV:N/AC:L/PR:N/UI:N) indicates trivial remote exploitation with no authentication. EPSS data not available; no confirmed active exploitation (not in CISA KEV). Vendor patch released in version 3.1.2.
Path normalization bypass in fast-uri 3.1.0 and earlier allows remote attackers to circumvent path-based access controls through percent-encoded path traversal sequences. The normalize() and equal() functions decode URL-encoded separators (%2F) and dot segments (%2E) before applying normalization rules, causing distinct URIs to collapse onto identical normalized paths. Applications relying on fast-uri for URL validation in authorization checks can be tricked into allowing access to restricted resources. EPSS exploitation probability not yet calculated given recent disclosure; no active exploitation confirmed (not in CISA KEV), but attack vector is trivial (CVSS AV:N/AC:L/PR:N/UI:N) and patch is available in version 3.1.1.