PT-2026-25863 · Go · Github.Com/Ctfer-Io/Romeo/Webserver

Published

2026-03-16

·

Updated

2026-03-16

·

CVE-2026-32805

CVSS v4.0
8.3
VectorAV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:L/SA:L

Summary

The 
sanitizeArchivePath
function in 
webserver/api/v1/decoder.go
(lines 80-88) is vulnerable to a path traversal bypass due to a missing trailing path separator in the 
strings.HasPrefix
check. A crafted tar archive can write files outside the intended destination directory.

Vulnerable Code

File: 
webserver/api/v1/decoder.go
, lines 80-88
func sanitizeArchivePath(d, t string) (v string, err error) {
	v = filepath.Join(d, t)
	if strings.HasPrefix(v, filepath.Clean(d)) {
		return v, nil
	}
	return "", &ErrPathTainted{
		Path: t,
	}
}
The function is called at line 48 inside 
[*Decompressor].Unzip
, which is invoked by 
Decode
(line 80) during execution of the webserver CLI (command 
download
).

Root Cause

strings.HasPrefix(v, filepath.Clean(d))
does not append a trailing 
/
to the directory prefix, causing a directory name prefix collision. If the destination is 
/home/user/extract-output
and a tar entry is named 
../extract-outputevil/pwned
, the joined path 
/home/user/extract-outputevil/pwned
passes the prefix check — it starts with 
/home/user/extract-output
— even though it is entirely outside the intended directory.

Steps to Reproduce

  1. Deploy Romeo. A measured app writes its coverage data.
  2. Place the PoC zip on the PVC. Any pod with write access to the 
    ReadWriteMany
    PVC (or the webserver itself) copies a 
    poc-path-traversal.tar
    into the 
    coverdir
    mount path. The archive contains legitimate coverage files alongside two crafted entries with path-traversal names.
  3. Run the webserver CLI against the running webserver:
webserver download 
 --server http://localhost:8080 
 --directory /home/user/extract-output
  1. Observe the bypass. 
    unzip
    processes the zip stream. For the malicious entries:
// entry name: ../extract-outputevil/poc-proof.txt
filepath.Join("/home/user/extract-output", "../extract-outputevil/poc-proof.txt")
 => "/home/user/extract-outputevil/poc-proof.txt"

strings.HasPrefix("/home/user/extract-outputevil/poc-proof.txt",
         "/home/user/extract-output")
 => true  // BUG: prefix collision; file lands OUTSIDE target dir
Both malicious entries are written outside 
/home/user/extract-output/
. The legitimate coverage files land correctly inside it.

Impact

Successful exploitation gives an attacker arbitrary file write on the machine running the webserver CLI. Real-world primitives include:
  • Overwriting 
    ~/.bashrc
    / 
    ~/.zshrc
    / 
    ~/.profile
    for RCE on next shell login
  • Appending to 
    ~/.ssh/authorized keys
    for persistent SSH backdoor
  • Dropping a malicious entry into 
    ~/.kube/config
    to hijack cluster access
  • Writing crontab entries for persistent scheduled execution
The attack surface is widened by the default 
ReadWriteMany
PVC access mode, which means any pod in the cluster with the PVC mounted can inject the payload — not just the Romeo webserver itself.

Fix

Path traversal

Weakness Enumeration

CWE-22

Related Identifiers

CVE-2026-32805
GHSA-P799-G7VV-F279

Affected Products

Github.Com/Ctfer-Io/Romeo/Webserver