CVE-2026-16158

Q: How do I fix CVE-2026-16158?

Upgrade fastify\/reply-from to 12.6.4 or later.

Q: Is CVE-2026-16158 being actively exploited?

Not that we know of. CVE-2026-16158 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.23% is the estimated probability that it will be exploited in the next 30 days. That is higher than 14% of all scored CVEs.

Q: How severe is CVE-2026-16158?

CVE-2026-16158 has a CVSS v3 base score of 8.7, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

Q: What does CVE-2026-16158 affect?

Published advisories record a fix for fastify\/reply-from (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

HIGH

8.7

CVSS v3

NVD

Description

Impact: @fastify/reply-from versions from 8.3.1 up to but not including 12.6.4 build the internal URL cache key by concatenating the destination and source path without a delimiter. Different destination and source pairs can therefore produce the same key while resolving to different upstream URLs. When getUpstream selects an upstream from request data, a URL cached for one upstream can be reused for a request intended for another upstream, causing cross-upstream data access and modification. The default configuration is affected. Setting disableCache to true prevents the behavior. Patches: upgrade to @fastify/reply-from 12.6.4. Workarounds: pass disableCache: true when registering the plugin.

CWE-441

How to fix

Remediation Available

fastify\/reply-fromNVD

Affected:>= 8.3.1, < 12.6.4Fixed in:12.6.4CVE-2026-16158derived from NVD

TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeChanged

Impact

ConfidentialityHigh

IntegrityHigh

AvailabilityNone

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

Exploit Intelligence

0.23%probability of exploitation in 30 days

14thpercentile

Low risk: more likely to be exploited than 14% of all known CVEs.

References

Vendor Advisory2

Related Vulnerabilities

Other CWE-441 vulnerabilities, ordered by exploit likelihood. View all

CVE	Severity	CVSS	EPSS	Exploited	Fix
CVE-2025-47269	High	8.3	38%	-	-
CVE-2019-3924	High	7.5	16%	-	Fix
CVE-2020-5412	Medium	6.5	10%	-	Fix
CVE-2019-3996	Medium	6.5	5.9%	-	-
CVE-2021-20042	Critical	9.8	2.7%	-	-
CVE-2019-1841	Medium	6.5	2.6%	-	Fix

Common questions

How do I fix CVE-2026-16158?

Upgrade fastify\/reply-from to 12.6.4 or later.

Is CVE-2026-16158 being actively exploited?

Not that we know of. CVE-2026-16158 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.23% is the estimated probability that it will be exploited in the next 30 days. That is higher than 14% of all scored CVEs.

How severe is CVE-2026-16158?

CVE-2026-16158 has a CVSS v3 base score of 8.7, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.

What does CVE-2026-16158 affect?

Published advisories record a fix for fastify\/reply-from (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.

Embed a live status badge for CVE-2026-16158

Markdown

[![CVE-2026-16158](https://tridentstack.com/cve/badge/CVE-2026-16158.svg)](https://tridentstack.com/cve/CVE-2026-16158)

HTML

<a href="https://tridentstack.com/cve/CVE-2026-16158"><img src="https://tridentstack.com/cve/badge/CVE-2026-16158.svg" alt="CVE-2026-16158"></a>

Find and fix vulnerabilities across your fleet

TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.

See how it works Start freeThis CVE lookup is free and always will be.

This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-08-05.