Vulnerability details
CVE-2026-27889
nats-io nats-server
NATS: Pre-auth remote server crash via WebSocket frame length overflow in wsRead
CVSS 3.1
7.5High
Official description
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. Starting in version 2.2.0 and prior to versions 2.11.14 and 2.12.5, a missing sanity check on a WebSockets frame could trigger a server panic in the nats-server. This happens before authentication, and so is exposed to anyone who can connect to the websockets port. Versions 2.11.14 and 2.12.5 contains a fix. A workaround is available. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points. If one is able to do so, a defense in depth of restricting either of these will mitigate the attack.
CVSS scores
| Score | Version | Source | Vector |
|---|---|---|---|
| 7.5High | 3.1 | CVEProject cvelistV5 (CNA) (GitHub_M) | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 7.5High | 3.1 | CVEProject cvelistV5 (CNA) (redhat-SADP) | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Affected products
| Vendor | Product | Versions | Source |
|---|---|---|---|
| nats-io | nats-server | >= 2.12.0, < 2.12.5 | CVEProject cvelistV5 (CNA) |
| nats-io | nats-server | >= 2.2.0, < 2.11.14 | CVEProject cvelistV5 (CNA) |
References and advisories
8- https://github.com/nats-io/nats-server/security/advisories/GHSA-pq2q-rcw4-3hr6 x_refsource_CONFIRM
- https://advisories.nats.io/CVE/secnote-2026-03.txt x_refsource_MISC
- https://access.redhat.com/security/cve/CVE-2026-27889 vdb-entryx_refsource_REDHAT
- https://bugzilla.redhat.com/show_bug.cgi?id=2451447 issue-trackingx_refsource_REDHAT
- https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27889.json x_sadp-csaf-vex
- https://access.redhat.com/errata/RHSA-2026:22347 vendor-advisoryx_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:23345 vendor-advisoryx_refsource_REDHAT
- https://access.redhat.com/errata/RHSA-2026:21769 vendor-advisoryx_refsource_REDHAT
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Details
- Published
- 2026-03-25
- Last updated
- 2026-09-09
- State
- Published
- Assigner (CNA)
- GitHub_M
Exploit prediction (EPSS)
0.59%
Probability of exploitation in 30 days
48.5%
Percentile (among all CVEs)
SSVC assessment (CISA)
- Automatable
- Yes
- Exploitation
- Proof of concept
- Technical impact
- Partial
Weaknesses (CWE)
- CWE-190Integer Overflow or Wraparound
- CWE-1286Improper Validation of Syntactic Correctness of Input