CVE-2026-27571
Medium · 5.9CVSS
5.9
EPSS
0.8%
Published
Feb 24, 2026
CISA due date
—
The record
NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging system. The WebSockets handling of NATS messages handles compressed messages via the WebSockets negotiated compression. Prior to versions 2.11.2 and 2.12.3, the implementation bound the memory size of a NATS message but did not independently bound the memory consumption of the memory stream when constructing a NATS message which might then fail validation for size reasons. An attacker can use a compression bomb to cause excessive memory consumption, often resulting in the operating system terminating the server process. The use of compression is negotiated before authentication, so this does not require valid NATS credentials to exploit. The fix, present in versions 2.11.2 and 2.12.3, was to bounds the decompression to fail once the message was too large, instead of continuing on. The vulnerability only affects deployments which use WebSockets and which expose the network port to untrusted end-points.
Affected packages
| Ecosystem | Package | Introduced | Fixed |
|---|---|---|---|
| Go | github.com/nats-io/nats-server | 0 | No fix |
| Go | github.com/nats-io/nats-server/v2 | 0 | 2.11.12 |
| Go | github.com/nats-io/nats-server/v2 | 2.12.0-RC.1 | 2.12.3 |
| Chainguard | k3s-1.32 | 0 | 1.32.12.1-r2 |
| Chainguard | k3s-1.33 | 0 | 1.33.8.1-r1 |
| Chainguard | k3s-static-1.32 | 0 | 1.32.12.1-r2 |
| Chainguard | k3s-static-1.33 | 0 | 1.33.8.1-r1 |
| Chainguard | kine | 0 | 0.14.12-r1 |
| Chainguard | nats-top | 0 | 0.6.3-r14 |
| Chainguard | nats-top-fips | 0 | 0.6.3-r13 |
| Chainguard | rke2-runtime-1.32 | 0 | 1.32.12.2.1-r3 |
| Chainguard | rke2-runtime-1.33 | 0 | 1.33.8.2.1-r3 |
| Chainguard | rke2-runtime-1.34 | 0 | 1.34.4.2.1-r3 |
| Chainguard | rke2-runtime-1.35 | 0 | 1.35.1.2.1-r3 |
| Chainguard | telegraf-1.36 | 0 | 1.36.4-r6 |
| Wolfi | k3s-1.32 | 0 | 1.32.12.1-r2 |
| Wolfi | k3s-1.33 | 0 | 1.33.8.1-r1 |
| Wolfi | k3s-static-1.32 | 0 | 1.32.12.1-r2 |
| Wolfi | k3s-static-1.33 | 0 | 1.33.8.1-r1 |
| Wolfi | kine | 0 | 0.14.12-r1 |
| Wolfi | nats-top | 0 | 0.6.3-r14 |
| Wolfi | telegraf-1.36 | 0 | 1.36.4-r6 |
| openSUSE:Leap 15.6 | govulncheck-vulndb | 0 | 0.0.20260226T182644-150000.1.149.1 |
Related vulnerabilities
- CVE-2022-29946 NATS.io NATS Server before 2.8.2 and Streaming Server before 0.24.6 could allow a remote… Also affects github.com/nats-io/nats-server
- CVE-2023-46129 NATS.io is a high performance open source pub-sub distributed communication technology… Also affects github.com/nats-io/nats-server/v2
- CVE-2026-35480 go-ipld-prime is an implementation of the InterPlanetary Linked Data (IPLD) spec… Also affects k3s-1.32
- CVE-2026-32241 Flannel is a network fabric for containers, designed for Kubernetes. Also affects k3s-1.32
- CVE-2026-32285 The Delete function fails to properly validate offsets when processing malformed JSON… Also affects k3s-1.32
- CVE-2026-33249 NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging… Also affects k3s-1.32
- CVE-2026-33248 NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging… Also affects k3s-1.32
- CVE-2026-33222 NATS-Server is a High-Performance server for NATS.io, a cloud and edge native messaging… Also affects k3s-1.32