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Fencer Vulns
medium 5.7

CVE-2023-28436 json

Non-interactive Tailscale SSH sessions on FreeBSD may use the effective group ID of the tailscaled process

published 2023-03-23 3 y ago modified 2026-09-10 1 mo ago also GHSA-vfgq-g5x8-g595 , GO-2023-1671 , EUVD-2023-1110

cvss
5.7
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 40%
public exploits
0
none known

Summary

Tailscale is software for using Wireguard and multi-factor authentication (MFA). A vulnerability identified in the implementation of Tailscale SSH starting in version 1.34.0 and prior to prior to 1.38.2 in FreeBSD allows commands to be run with a higher privilege group ID than that specified in Tailscale SSH access rules. A difference in the behavior of the FreeBSD `setgroups` system call from POSIX meant that the Tailscale client running on a FreeBSD-based operating system did not appropriately restrict groups on the host when using Tailscale SSH. When accessing a FreeBSD host over Tailscale SSH, the egid of the tailscaled process was used instead of that of the user specified in Tailscale SSH access rules.

Tailscale SSH commands may have been run with a higher privilege group ID than that specified in Tailscale SSH access rules if they met all of the following criteria: the destination node was a FreeBSD device with Tailscale SSH enabled; Tailscale SSH access rules permitted access for non-root users; and a non-interactive SSH session was used.

Affected users should upgrade to version 1.38.2 to remediate the issue.

Patch / fix

  • go tailscale.com 1.38.2
  • tailscale tailscale 1.38.2

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
20 mo ago

Exploit prediction

0.46% chance of exploitation in the next 30 days, higher than 40% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 5.7 CVSS:3.1/AV:A/AC:L/PR:H/UI:R/S:C/C:H/I:N/A:N
NVD 3.1 8.0 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
GitHub 3.0 5.7 CVSS:3.0/AV:A/AC:L/PR:H/UI:R/S:C/C:H/I:N/A:N

Affected packages

ecosystem package affected fixed in
go tailscale.com
>=1.34.0, <1.38.2
1.38.2

Affected products

  • tailscale tailscale

Classification

Weakness
  • CWE-269 Improper Privilege Management

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.