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Debian LinuxOperating system · Debian

CVE-2017-17458

CRITICAL · 9.8 CVSS v3.0 Published 2017-12-07
Fix available
A fix is available. Upgrade to 4.4.1 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
In Mercurial before 4.4.1, it is possible that a specially malformed repository can cause Git subrepositories to run arbitrary code in the form of a .git/hooks/post-update script checked into the repository. Typical use of Mercurial prevents construction of such repositories, but they can be created programmatically.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

A vulnerability in Mercurial before 4.4.1 allows specially crafted malicious repositories to execute arbitrary code via Git subrepositories. When Mercurial processes a malformed repository containing Git subrepos, it can trigger execution of a .git/hooks/post-update script that was checked into the repository.

MitigationUpgrade Mercurial to version 4.4.1 or later. Avoid cloning or pulling from untrusted repositories until the update is applied.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Debian LinuxOperating system
Affected:= 7.0= 8.0
MercurialApplication
Affected:< 4.4.1

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check installed Mercurial version
    Run `hg --version` and parse the version number from the output. Compare it to 4.4.1.
    Affected if The version number is less than 4.4.1 (for example, 4.4.0, 4.3.x, or earlier).
  2. Verify subrepository support is enabled
    Check the Mercurial configuration file (typically in ~/.hgrc or /etc/mercurial/hgrc) for the subrepos extension. Run `hg config extensions` to list loaded extensions and look for subrepos or subrepo-related entries.
    Affected if The subrepos extension is loaded or subrepositories are used in any existing repository clones.
  3. Inspect existing cloned repositories for Git subrepos
    Look for `.hgsubstate` or `.hgsub` files in local repository working directories. Search for entries starting with `git:` within `.hgsub` files which indicate Git subrepositories.
    Affected if Any cloned repository contains `.hgsub` with `git:` entries pointing to external Git repositories.
  4. Assess exposure to untrusted repositories
    Review which remote repositories users have cloned or pulled from. Check if repositories from untrusted or public sources (such as open-source hosting sites) are present in the environment.
    Affected if Users have cloned or pulled repositories from untrusted sources that could contain malicious Git subrepos with crafted hooks.

You are affected if Mercurial version is below 4.4.1 AND your environment contains or may clone repositories with Git subrepositories from untrusted sources.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 4.4.1 or later
Fixed in 4.4.1
Interim mitigation

Upgrade Mercurial to version 4.4.1 or later. Avoid cloning or pulling from untrusted repositories until the update is applied.

Recommended fix High confidence

Mercurial 4.4.1 or later

  1. 1. Check current Mercurial version by running: hg --version
  2. 2. For source installations: Download Mercurial 4.4.1 or later from https://www.mercurial-scm.org/downloads
  3. 3. Extract the archive and navigate to the directory: tar -xzf mercurial-4.4.1.tar.gz && cd mercurial-4.4.1
  4. 4. Install the upgraded version: python setup.py install (or use pip: pip install -U mercurial>=4.4.1)
  5. 5. Verify the upgrade was successful by running: hg --version and confirm the version is 4.4.1 or later
  6. 6. For Debian systems: Run apt-get update && apt-get install mercurial to install the patched version from Debian security updates
Caveat Minor: Review release notes for any changes to hook behavior or subrepository handling that may affect existing workflows

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2017-17458 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data