CyberSecBulletin
CVE-2023-45283NVD status: Modified

path/filepath: Improper Limitation of a Pathname to a Restricted Directory

Published Updated By the CyberSecBulletin desk

CVE-2023-45283 is a high-severity improper limitation of a pathname to a restricted directory vulnerability in path/filepath from Go standard library, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 1.20.11, 1.21.4, 1.20.12 as the first without the flaw, so updating path/filepath to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 3.35% chance of exploitation within 30 days, higher than 89% of scored CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Update path/filepath to 1.20.11 or 1.21.4 or 1.20.12 or 1.21.5, whichever matches your release line, or a later version.
  2. Update internal/safefilepath to 1.20.11 or 1.21.4, whichever matches your release line, or a later version.
  3. Update Go to 1.20.11 or 1.21.4, whichever matches your release line, or a later version.
  4. Read the advisory on go.dev for workarounds and exact fixed builds.
  5. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
Go standard librarypath/filepathbefore 1.20.11; 1.21.0-0 up to, but not including, 1.21.4; 1.20.11 up to, but not including, 1.20.12; 1.21.4 up to, but not including, 1.21.51.20.11, 1.21.4, 1.20.12, 1.21.5
Go standard libraryinternal/safefilepathbefore 1.20.11; 1.21.0-0 up to, but not including, 1.21.41.20.11, 1.21.4
GoGobefore 1.20.11; 1.21.0-0 up to, but not including, 1.21.41.20.11, 1.21.4

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
NoneNothing can be modified.
Availability
NoneAvailability is not affected.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N. Scored by NVD.

Official description

The filepath package does not recognize paths with a \??\ prefix as special. On Windows, a path beginning with \??\ is a Root Local Device path equivalent to a path beginning with \\?\. Paths with a \??\ prefix may be used to access arbitrary locations on the system. For example, the path \??\c:\x is equivalent to the more common path c:\x. Before fix, Clean could convert a rooted path such as \a\..\??\b into the root local device path \??\b. Clean will now convert this to .\??\b. Similarly, Join(\, ??, b) could convert a seemingly innocent sequence of path elements into the root local device path \??\b. Join will now convert this to \.\??\b. In addition, with fix, IsAbs now correctly reports paths beginning with \??\ as absolute, and VolumeName correctly reports the \??\ prefix as a volume name. UPDATE: Go 1.20.11 and Go 1.21.4 inadvertently changed the definition of the volume name in Windows paths starting with \?, resulting in filepath.Clean(\?\c:) returning \?\c: rather than \?\c:\ (among other effects). The previous behavior has been restored.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Improper Limitation of a Pathname to a Restricted Directory

The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

How developers prevent this class of flaw

  • For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.
  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
  • Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth.

More Improper Limitation of a Pathname to a Restricted Directory vulnerabilities (CWE-22)

Timeline

  1. CVE record published.
  2. Record last changed materially (score, affected products, status or references).

References

Advisories

Other vulnerabilities in path/filepath

All path/filepath vulnerabilities

Recent Improper Limitation of a Pathname to a Restricted Directory vulnerabilities

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