Medium

Next.js RSC and HTML cache confusion

IdentifiersCVE-2026-44576CWE-444

CVE-2026-44576 is a cache poisoning vulnerability in Next.js affecting applications from 14.2.0 to before 15.5.16 and 16.2.5 that use React Server Components (RSC). Under affected conditions, shared caches can fail to correctly partition response variants for the same URL, causing confusion between RSC payload responses and normal HTML document responses. An attacker can trigger an RSC response to be cached under the original URL and subsequently cause that poisoned shared cache entry to be served to later users, who receive component payload data instead of the expected HTML page. The issue is described as an RSC and HTML cache confusion flaw and depends on intermediary caching behavior rather than a purely application-local condition.

For your environment

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ANALYST BRIEF

Impact, mitigation & remediation

What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.

Impact

What an attacker gets, and what they’ve been doing with it.

Successful exploitation allows poisoning of shared cache entries for affected Next.js routes. Subsequent visitors may be served React Server Component payloads in place of the intended HTML document for the original URL. This can cause content corruption, application malfunction, and denial of normal page rendering for downstream users. In environments with shared intermediary caches such as CDNs or reverse proxies, the impact extends beyond a single requester and can affect multiple users until the poisoned cache entry expires or is purged.

Mitigation

If you can’t patch tonight, do this now.

If immediate upgrade is not possible, ensure shared caches correctly separate RSC and HTML response variants by keying on the relevant RSC request headers and honoring the Vary header. Disable or bypass shared caching for affected App Router and React Server Component responses where correct variant partitioning cannot be guaranteed. Restrict or review CDN and reverse-proxy cache rules for routes serving mixed response types, and purge existing cache entries for affected URLs.

Remediation

Patch, then assume compromise.

Upgrade Next.js to a fixed release. The vulnerability is fixed in 15.5.16 and 16.2.5. Affected deployments should move to 15.5.16 or later on the 15.x line, or 16.2.5 or later on the 16.x line, as applicable. After upgrading, purge CDN and reverse-proxy caches to remove any poisoned entries that may already exist.

PUBLIC EXPLOITS

Exploits

No valid public exploits. Mallory filtered out 1 candidate as fakes, detection scripts, or README-only repos.

VALID 0 / 1 TOTALView more in app

All candidate exploits were filtered out by Mallory's validation.

EXPOSURE SURFACE

Affected products & vendors

Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.

VendorProductType

VercelNextapplication

VercelNext.Jsapplication

Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.

ACTIVITY FEED

Recent activity

2 sources tracked across advisories and community write-ups. News coverage will land here when it surfaces.

2 SOURCESView more in app

No news coverage yet. Advisories and community discussion only.

What this page doesn’t show

The version that knows your environment.

This page is what’s public. Mallory adds the parts that aren’t: which of your assets are affected, which adversaries are exploiting it right now, which detections to deploy, and what to do tonight.

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Exposure mapping

Query your assets running an affected version, and investigate the blast radius.

Threat actor evidence

Every observed campaign linking this CVE to a named adversary.

Associated malware

Malware families riding this exploit, with evidence and IOCs.

Detection signatures

YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.

Vendor-by-vendor mapping

Cross-references every affected SKU, including bundled OEM variants.

Social activity2

Community discussion across Reddit, Mastodon, and other social sources.

EXTERNAL REFERENCES

MITRE CVE

cve.org · CVE-2026-44576

NVD

nvd.nist.gov/vuln/detail/CVE-2026-44576

MITRE CWE · CWE-444

cwe.mitre.org

Vendor Advisory

github.com/vercel/next.js/security/advisories/GHSA-wfc6-r584-vfw7