CVE.org (no NVD analysis yet)· CNA openjs

CVE-2026-120213: @fastify/http-proxy vulnerable to prefix escape via decoded route parameters

CriticalCVSS 9.1 · v3.1—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 36/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.69% (FIRST EPSS); higher than 53.2% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
Fixed version: @fastify/http-proxy @fastify/http-proxy 11.6.6.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to @fastify/http-proxy @fastify/http-proxy 11.6.6 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

@fastify/http-proxy is a Fastify plugin that proxies HTTP requests to an upstream server under a configured prefix. In versions 9.0.0 through 11.6.5, when an application uses parameterized prefix and rewritePrefix options to pin clients to a fixed upstream path, the plugin substitutes URL-decoded route parameters into rewritePrefix without re-encoding them. A parameter value that encodes a path separator together with a fragment or query delimiter therefore decodes into real separators and delimiters that inject extra upstream path segments and strip the mandatory suffix the rewritePrefix was meant to enforce, without using any dot-dot traversal. An unauthenticated remote attacker can use this to reach upstream locations outside the intended prefix, leading to path-restriction bypass and, depending on the upstream, server-side request forgery or authorization bypass in the proxied service. The issue is fixed in @fastify/http-proxy 11.6.6, and users should upgrade to 11.6.6 or later. There is no workaround other than upgrading.

EUVD-2026-115117

Published: Nov 2, 2026
Updated: Nov 2, 2026
EPSS: 0.6% · 53th percentile
CWE: CWE-22

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 36 / 40 · 9.1 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.6%

CISA SSVC decision

Exploitation: none
Automatable: yes
Technical impact: total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: —
CNA · openjs: 9.1; NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Is your version affected? Check it

Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

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Versions reported by the vendor

Affected version ranges reported by the assigning authority (openjs). Independent of NVD's CPE analysis and usually ahead of it.

@fastify/http-proxy @fastify/http-proxy
- 11.6.6not affected
- 9.0.0 and later · before 11.6.6affected · semver

Same product

Other highest-scoring records for the same primary product.

CVE-2026-120214@fastify/http-proxy vulnerable to prefix escape via percent-encoded backslash dot-segments
23Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
@fastify/http-proxy @fastify/http-proxy	11.6.6	Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

PublishedNov 2, 2026
Fix recordedNov 2, 2026same day
TodayNov 12, 2026+10 d

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Panelv4reporter
UlisesGasconremediation developer
mcollinaremediation developer

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2026-1202140 days apart@fastify/http-proxy vulnerable to prefix escape via percent-encoded backslash dot-segments
23Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-26-1447 · Nov 3, 2026(Fastify Güvenlik Zafiyeti)

All national notices →

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: high · data can be read
Integrity: high · data or configuration can be modified
Availability: none

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
Availability impact: None

Weakness class (CWE)

CWE-22 · Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

CVSS vector

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

nvd-secondary

Root cause

A user-supplied file name is joined with the allowed directory, but the result is never checked to confirm it is still inside that directory.

The bug in code

The whole CWE-22 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1const file = path.join(ROOT, req.query.name);
2res.sendFile(file);

Fixed

1const file = path.resolve(ROOT, req.query.name);
2if (!file.startsWith(ROOT + path.sep)) {
3  return res.sendStatus(400);
4}
5res.sendFile(file);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

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Change log

SSVC exploitation— → noneNov 2, 2026, 7:07 PM UTC
Exploit maturity— → noneNov 2, 2026, 12:09 PM UTC
Fix✗ → ✓Nov 2, 2026, 12:09 PM UTC

For records you follow, these changes also arrive as notifications. →

References

cna.openjsf.org/security-advisories.html

Show all references (1 more)

github.com/fastify/fastify-http-proxy/security/advisories/GHSA-h3vp-4jfr-v364

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records