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Fencer Vulns
high 7.5

CVE-2020-26521 json

Nil dereference in NATS JWT causing DoS of nats-server

published 2020-11-06 6 y ago modified 2026-09-10 1 mo ago also GHSA-h2fg-54x9-5qhq , GHSA-hmm9-r2m2-qg9w , GO-2022-0402 , EUVD-2022-1028

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
2.2%
EPSS 2.2% chance of exploitation in 30 days, percentile 82%
public exploits
0
none known

Summary

The JWT library in NATS nats-server before 2.1.9 allows a denial of service (a nil dereference in Go code).

Patch / fix

  • go github.com/nats-io/nats-server/v2 2.1.9
  • go github.com/nats-io/jwt 1.1.0
  • linuxfoundation nats-server 2.1.9
  • golang-github-nats-io-jwt Debian 14, Debian 13, Debian 12 2.2.0-1

debian advisories DEBIAN-CVE-2020-26521

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2020-26521 updated cvss 7.5

nats-server: nil dereferences in JWT library causing Go panic

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

2.16% chance of exploitation in the next 30 days, higher than 82% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 5.0 AV:N/AC:L/Au:N/C:N/I:N/A:P
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
go github.com/nats-io/nats-server/v2
<2.1.9
2.1.9
go github.com/nats-io/jwt
<1.1.0
1.1.0

Classification

Weakness

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.