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SubversionApplication · Apache

CVE-2016-2167

MEDIUM · 6.8 CVSS v3.0 Published 2016-05-05
Fix available
A fix is available. Upgrade to after 1.8.15 or later.
See remediation →
74/100
Remediation priority · Elevated
Remotely reachable 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
The canonicalize_username function in svnserve/cyrus_auth.c in Apache Subversion before 1.8.16 and 1.9.x before 1.9.4, when Cyrus SASL authentication is used, allows remote attackers to authenticate and bypass intended access restrictions via a realm string that is a prefix of an expected repository realm string.

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

The canonicalize_username function in svnserve's Cyrus SASL authentication implementation incorrectly performs prefix matching on realm strings rather than exact matching. This allows remote attackers to authenticate by providing a realm string that is a prefix of the actual repository realm, bypassing intended access restrictions.

MitigationUpgrade Apache Subversion to version 1.8.16 or 1.9.4 or later to obtain the fixed code. If patching is not immediately feasible, disable Cyrus SASL authentication or implement compensating network-level access controls.

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
SubversionApplication
Affected:<= 1.8.15= 1.9.0= 1.9.1= 1.9.2= 1.9.3

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
High
Privileges
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
None

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

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 svnserve version
    Run 'svnserve --version' and note the version number in the output
    Affected if The version is 1.8.15 or earlier, or 1.9.0 through 1.9.3 inclusive
  2. Verify Cyrus SASL is in use
    Check repository configuration files (svnserve.conf) and SASL configuration files in the conf directory or system SASL directory (often /etc/sasl2/) for 'sasl' or 'pwcheck' settings
    Affected if Cyrus SASL authentication is configured and enabled for the repository
  3. Inspect realm configuration
    Look for 'realm' or 'realm_name' settings in the repository's svnserve.conf or SASL configuration files
    Affected if A repository realm is defined and Cyrus SASL is enabled - the prefix matching flaw can be exploited against this realm

You are affected if you run a vulnerable Subversion version (1.8.15 or earlier, or 1.9.0-1.9.3) with Cyrus SASL authentication enabled for svnserve.

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.

From vendor data
Upgrade available Upgrade to a release after 1.8.15
Interim mitigation

Upgrade Apache Subversion to version 1.8.16 or 1.9.4 or later to obtain the fixed code. If patching is not immediately feasible, disable Cyrus SASL authentication or implement compensating network-level access controls.

Fix this in Subversion Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.

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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-2016-2167 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