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Fencer Intel
medium 6.5

CVE-2024-8158 json

User impersonation for lib9p based 9p fileservers

published 2y ago modified 4mo ago also EUVD-2024-48983

cvss
6.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 32%
public exploits
0
none known

Summary

A bug in the 9p authentication implementation within lib9p allows an attacker with an existing valid user within the configured auth server to impersonate any other valid filesystem user.

This is due to lib9p not properly verifying that the uname given in the Tauth and Tattach 9p messages matches the client UID returned from the factotum authentication handshake.

The only filesystem making use of these functions within the base 9front systems is the experimental hjfs disk filesystem, other disk filesystems (cwfs and gefs) are not affected by this bug.

This bug was inherited from Plan 9 and is present in all versions of 9front and is remedied fully in commit 9645ae07eb66a59015e3e118d0024790c37400da.

Patch / fix

  • 9front 9front 9645ae07eb66a59015e3e118d0024790c37400da

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CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
2y ago

Exploit prediction

0.38% chance of exploitation in the next 30 days, higher than 32% of all scored CVEs (FIRST EPSS, 2026-11-11).

CVSS scores

assigned by version score vector
CNA 4.0 8.8 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/AU:N/V:C/RE:L/U:Red
CNA 4.0 8.8 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:N/R:X/V:C/RE:L/U:Red
NVD 3.1 6.5 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

Affected products

  • 9front 9front

Classification

Weakness
  • CWE-639 Authorization Bypass Through User-Controlled Key

References

Sources

Fencer Intel 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.