bytecode-viewer: Improper Limitation of a Pathname to a Restricted Directory
CVE-2022-21675 is a high-severity improper limitation of a pathname to a restricted directory vulnerability in bytecode-viewer from Konloch, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an unauthenticated attacker, but only if a user takes part, for example by opening a link or file. Affected bytecode-viewer versions: < 2.11.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 3.22% chance of exploitation within 30 days, higher than 88% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Check which version of bytecode-viewer you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Konloch | bytecode-viewer | < 2.11.0 | Not stated |
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
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- RequiredA user must take an action such as opening a file or link.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 9.9 | Critical | CNA (github.com) |
| CVSS 3.1 | 7.8 | High | NVD |
| CVSS 2.0 | 6.8 | Medium | NVD |
Official description
Bytecode Viewer (BCV) is a Java/Android reverse engineering suite. Versions of the package prior to 2.11.0 are vulnerable to Arbitrary File Write via Archive Extraction (AKA "Zip Slip"). The vulnerability is exploited using a specially crafted archive that holds directory traversal filenames (e.g. ../../evil.exe). The Zip Slip vulnerability can affect numerous archive formats, including zip, jar, tar, war, cpio, apk, rar and 7z. The attacker can then overwrite executable files and either invoke them remotely or wait for the system or user to call them, thus achieving remote command execution on the victim’s machine. The impact of a Zip Slip vulnerability would allow an attacker to create or overwrite existing files on the filesystem. In the context of a web application, a web shell could be placed within the application directory to achieve code execution. All users should upgrade to BCV v2.11.0 when possible to receive a patch. There are no recommended workarounds aside from upgrading.
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
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
- github.com/Konloch/bytecode-viewer/security/advisories/GHSA-3wq9-j4fc-4wmcThird Party Advisory
Patches and release notes
- github.com/Konloch/bytecode-viewer/commit/1ec02658fe6858162f5e6a24f97928de6696c5cbThird Party Advisory
- github.com/Konloch/bytecode-viewer/commit/c968e94b2c93da434a4ecfac6d08eda162d615d0Third Party Advisory
- github.com/Konloch/bytecode-viewer/releases/tag/v2.11.0Release Notes, Third Party Advisory
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