Security Digest · Vulnerability record
CVE-2026-49252: deepstream is vulnerable to prototype pollution
deepstream is a server that allows clients and backend services to sync data, send messages and make rpcs at scale.
CVSS 9.9 Critical EPSS 0.5% · p40
Should you act?
Critical, preconditions apply
Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.5%, percentile 40: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 40% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Needs an account (low (any account)). Exposure depends on who can log in.
- Only applies if your dependency tree includes
@deepstream/server(npm) < 10.0.5, fixed in 10.0.5. Check your lockfile, including transitive dependencies.
What it is
deepstream is a server that allows clients and backend services to sync data, send messages and make rpcs at scale. Versions prior to 10.0.5 are vulnerable to Prototype Pollution. Exploitation can lead to potential privilege escalation from any authenticated user with write permission to any record. This issue has been fixed in version 10.0.5.
From the GitHub advisory
Impact Prototype pollution in deepstream server v
Patches Yes, upgrade to v10.0.5
Workarounds Filter out all messages containing the path proto, constructor, prototype, before they reach the server's message pipeline
Weakness type: CWE-1321.
Product: @deepstream/server (npm) · Assigned by: GitHub_M · Published: 2026-06-18
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| npm | @deepstream/server | < 10.0.5 | 10.0.5 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| deepstreamIO | deepstream.io | < 10.0.5 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| GitHub_M | 3.1 | 9.9 Critical | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L |
| GitHub | 3.1 | 9.9 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:L |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: low (any account)
- User interaction: none
- Scope: changed (can affect other components)
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation none, automatable no, technical impact partial.
- FIRST EPSS (model of 2026-10-21): 0.47% probability of exploitation activity in the next 30 days; percentile 40.
Timeline
- — CVE record published by GitHub_M
- — CVE record last updated
- — GitHub-reviewed advisory GHSA-9v98-6g37-x9g6 published (critical)
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vulnerability records
- GitHub Advisory GHSA-9v98-6g37-x9g6 github.com
- CVE.org record CVE-2026-49252 cve.org
- NVD entry CVE-2026-49252 nvd.nist.gov
Other references from the CVE record and advisory
- github.com github.com
- github.com github.com