CVE-2026-16158

8.7 HIGH 0.4% exploit odds Fix listed Other Web app

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure, data tampering.
Exploit odds: 0.4% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-07-18 13:17 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-08-05 19:46 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.4% in the next 30 days (EPSS).
Severity: 8.7 HIGH (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-07-18 13:17 UTC
Last modified: 2026-08-05 19:46 UTC
Exploit probability: 0.4% · EPSS, next 30 days
Weakness: CWE-441
Record status: Analyzed

Affected

Fastify fastify\/reply-from < 12.6.4

Attack profile CVSS 3.1 · 8.7

Attack vector: Network
Complexity: High
Privileges needed: None
User interaction: None
Scope: Changed
Confidentiality: High
Integrity: High
Availability: None

Raw vector

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

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-16158.md and follow it. Check whether this project is affected by CVE-2026-16158. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record