How severe is CVE-2026-27804?

No CVSS score has been assigned to CVE-2026-27804 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-27804?

CVE-2026-27804 affects the following packages: parse-server (npm), parse-server (npm). Ecosystems affected: npm.

How do I fix CVE-2026-27804?

Update parse-server to 9.3.1-alpha.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27804 is resolved across your whole dependency graph.

How do I detect CVE-2026-27804 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for parse-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-27804 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Is CVE-2026-27804 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-27804 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-27804?

CVE-2026-27804 has an EPSS (Exploit Prediction Scoring System) score of 0.2%, placing it in the 14th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-27804?

CVE-2026-27804 is classified as Broken Cryptographic Algorithm (CWE-327), CWE-345 (CWE-345). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-27804 published, and has it been updated?

CVE-2026-27804 was published on February 25, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-27804 — parse-server

Fix: parse-community/parse-server@9b94083

CVE-2026-27804 is a Broken Cryptographic Algorithm vulnerability in parse-server. A fix is available for parse-server — see the affected versions and patch details below.

Parse Server: Account takeover via JWT algorithm confusion in Google auth adapter

Also known asBIT-parse-2026-27804GHSA-4q3h-vp4r-prv2

Published

Feb 25, 2026

Updated

Aug 12, 2026

Affected

2 pkgs

Patched

2 / 2

Exploits

None indexed

Exploitation data as of Oct 22, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
A successful exploit gives an attacker total control of the affected component, not partial access.
CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-27804.

EPSS Exploitation Probability

via FIRST.org ↗

0.2%probability of exploitation in next 30 days

Lower Risk+0.01%

Lower risk than most CVEs14th percentile — riskier than 14% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

2 pkgs affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

62other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

parse-servernpm

38Kdownloads / week

Description

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.3 and 9.1.1-alpha.4, an unauthenticated attacker can forge a Google authentication token with alg: "none" to log in as any user linked to a Google account, without knowing their credentials. All deployments with Google authentication enabled are affected. The fix in versions 8.6.3 and 9.1.1-alpha.4 hardcodes the expected RS256 algorithm instead of trusting the JWT header, and replaces the Google adapter's custom key fetcher with jwks-rsa which rejects unknown key IDs. As a workaround, dsable Google authentication until upgrading is possible.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`parse-server`	≥ 9.0.0&&< 9.3.1-alpha.4	9.3.1-alpha.4`npm install parse-server@9.3.1-alpha.4`
📦npm	`parse-server`	all versions	8.6.3`npm install parse-server@8.6.3`

Affected Products

1 product · 5 configurations

Application

parse-serverparseplatform

≥ 9.0.0 && < 9.3.1

1 version

9.3.1

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for parse-server, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update parse-server to 9.3.1-alpha.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27804 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

Frequently Asked Questions

Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to versions 8.6.3 and 9.1.1-alpha.4, an unauthenticated attacker can forge a Google authentication token with `alg: "none"` to log in as any user linked to a Google account, without knowing their credentials. All deployments with Google authentication enabled are affected. The fix in versions 8.6.3 and 9.1.1-alpha.4 hardcodes the expected `RS256` algorithm instead of trusting the JWT header, and replaces the Google adapter's custom key fetcher with `jwks-rsa` which rejects unknown key

O3 Security · Impact-Aware SCA

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