PT-2026-89202 · Pypi · Githacker

CVE-2026-50024

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Published

2026-09-09

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Updated

2026-09-10

CVSS v3.1

5.3

Medium

VectorAV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Summary

GitHacker through 1.1.7 did not validate path segments parsed from attacker-controlled .git/HEAD before joining them onto its output directory. A malicious server could coerce GitHacker into reading arbitrary local files. Contents do not stream back wholesale, but the recovery loop turns any 40-character hex substring into an outbound HTTP GET — an existence oracle for arbitrary paths plus hex-fragment exfiltration of file contents.

Details

Vulnerability

GitHacker rebuilds a remote .git/ by fetching files into temp dst. Two functions derived filesystem paths from server-controlled content:
  • add head file tasks reads the downloaded .git/HEAD, parses ref: <ref-path>, and joins the raw ref-path onto temp dst/.git/logs/ before reading the resulting file.
  • add hashes parsed scans any file it reads for 40-character hex substrings and emits GET .git/objects/<sha[0:2]>/<sha[2:]> for each one — onto the attacker's server and into the local output tree.
Pre-fix, add head file tasks did not validate the ref segments. A malicious .git/HEAD of
ref: ../../../../../../etc/passwd
caused add head file tasks to traverse out of temp dst and read /etc/passwd. The bytes flowed into add hashes parsed, which emitted one outbound HTTP request per 40-char-hex match — observable on the attacker's logs.

Impact

PR #65 originally classified this as arbitrary local file read. Joint analysis during coordinated disclosure narrowed the primitive: file contents do not stream back wholesale because the only egress channel is the 40-char-hex regex. In practice an attacker can:
  • Existence oracle for any path on the GitHacker host (/etc/shadow, /root/.ssh/id rsa, /home/<user>/.git-credentials, build artifacts under /tmp/).
  • Hex-fragment exfiltration when the targeted file contains 40-char hex sequences: other git repos' refs / pack filenames, password hashes, HMAC-SHA1 outputs, some session tokens.
Not exploitable without victim action: the attacker must persuade the victim to run GitHacker against a URL they control. Project guidance has always been to run GitHacker inside a disposable container.

Scoping note: no write-side primitive in 1.1.7

A working write-side primitive (attacker drops content outside temp dst via add folder / add task) does not reproduce against the shipped 1.1.7 source. Empirical testing by the reporter against GitHacker-1.1.7.tar.gz (25 traversal-style payloads including ....//, %2e%2e%2f, layered foo/../../, NUL bytes, backslash variants, absolute paths) yielded 0/25 escapes. Two structural reasons:
  1. add folder anchors every derived path on self.url + '.git/', so the first path component after the url length strip is always .git. os.path.join's absolute-path short-circuit never fires.
  2. Python's str.replace("..", "") is greedy non-overlapping; ....// collapses to //, ......// to ///, etc. No literal .. survives into add task.
5f2a8ba is still the correct fix for the read-side primitive and additionally hardens add task as defense in depth against future regressions — for example, if a later caller removes the .git/ anchor in add folder or wires a new server-controlled segment source into add task.

Fix

Commit 5f2a8ba introduces is safe path segment as a single trust boundary: every segment about to be joined onto temp dst or appended to an outgoing URL is validated against an allowlist before add task accepts it. Empty / . / .. / separators / NUL / control characters are rejected; the brittle replace("..", "") filter is removed.
The fix also tightens adjacent surfaces preemptively:
  • add folder switches to urlparse-based scheme + netloc + path comparison.
  • construct url from path components percent-encodes every segment.
PR #65's two-layer defense (allowlist regex + os.path.realpath() confinement) was consolidated onto the allowlist applied at queue-time, removing the TOCTOU window an after-the-fact realpath() check leaves open and the per-call-site drift risk. PR #65 was closed in favour of the broader fix.
Regression tests in [tests/test ref validation.py](https://github.com/WangYihang/GitHacker/blob/main/tests/test ref validation.py) (commit 16fcd81) pin the PoC and six bypass variants (extra-depth, mid-path, NUL, absolute path, leading-dot, .lock-suffix).

Credit

Reported and patched-prototyped by Zac Wang (@7a6163) in #65. Zac refined the impact framing from "arbitrary file read" to "existence oracle + hex-fragment exfiltration" and verified the absence of a write-side primitive against the shipped 1.1.7 sdist with a 25-payload harness.

Patches

Patched in 1.1.8 (commit 5f2a8ba; tests 16fcd81).

Workarounds

Run GitHacker inside a disposable container. Do not point GitHacker at any URL whose contents are not under your control.

Resources

Fix

Path traversal

Relative Path Traversal

Found an issue in the description? Have something to add? Feel free to write us 👾
dbugs@ptsecurity.com

Weakness Enumeration

CWE-22CWE-23

Related Identifiers

CVE-2026-50024
GHSA-HR3M-4QWQ-3MGC
PYSEC-2026-3835

Affected Products

Githacker