shallow-backup · GitPython: Incomplete unsafe_git_clone_options denylist omits --template enabling arbitrary command execution via
Affects shallow-backupSource GCVE Database
Not known to be exploited · CVSS 7.7 High : upgrade to 6.6_4 soon.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.8% chance of exploitation in 30 days – higher than 57% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.6_4
CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 13 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Upgrade shallow-backup to 6.6_4.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Homebrewshallow-backuppkg:brew/shallow-backupOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
Description
## Summary GitPython's `unsafe_git_clone_options` denylist omits `--template`. `git clone --template=<dir>` copies `<dir>/hooks/` into the new repository and runs them (`post-checkout` fires during clone), so a caller who can influence clone options can achieve arbitrary command execution in the default `allow_unsafe_options=False` configuration. ## Root Cause `base.py:145-152` defines `unsafe_git_clone_options = ["--upload-pack","-u","--config","-c"]` — `--template` is absent. The guard candidate `['--template']` passes `check_unsafe_options` (verified). git copies the hook directory and executes `post-checkout` at checkout time. git's `protocol.allow`/`GIT_ALLOW_PROTOCOL` do not gate `--template`; the incomplete denylist is the only defense. ## Impact Arbitrary OS command execution during clone (default config). Requires an attacker-readable directory containing an executable hook — a genuine second precondition (realistic via shared filesystems, upload dirs, `/tmp`, or attacker-writable network paths), reflected as AC:H. ## Proof of Concept ```python # attacker stages <dir>/hooks/post-checkout (chmod +x) from git import Repo Repo.clone_from(src, dst, template='<dir>') # post-checkout hook executes -> marker created (verified) ``` ## Attack Chain 1. Setup: attacker stages `<dir>/hooks/post-checkout` (chmod +x). Guard: n/a (filesystem). 2. Entry: `Repo.clone_from(url, path, template='<dir>')`. Guard: `check_unsafe_options(candidates=['--template'], unsafe=unsafe_git_clone_options)`. Bypass proof: `--template` not on the denylist -> passes (verified candidate `['--template']`, no error). 3. Sink: git copies the hook and executes `post-checkout` at checkout. Impact: ACE, default config (verified marker created). ## Bypass Evidence Live-verified on HEAD (tag 3.1.53): guard candidate `['--template']` passed with no error; staged `post-checkout` hook executed during `clone_from`, creating the marker. Independent of the value-smuggle bypass (`--template` is a legitimate long option that survives any single-char-value fix). Not covered by any existing advisory. ## Affected Versions `<= 3.1.53` ## Suggested Fix Add `--template` (and audit for other hook/exec-influencing options) to `unsafe_git_clone_options`. --- Reported by **zx (Jace)** — GitHub: @manus-use
References
- github.com/gitpython-developers/GitPython/security/advisories/GHSA-6p8h-3wgx-97gf (opens in a new tab)
- github.com/gitpython-developers/GitPython/pull/2180 (opens in a new tab)
- github.com/gitpython-developers/GitPython/commit/ffcb5359e87619f4fe4a70a4aff5f08c5580ba97 (opens in a new tab)
- github.com/gitpython-developers/GitPython (opens in a new tab)
- github.com/gitpython-developers/GitPython/releases/tag/3.1.54 (opens in a new tab)