CVE-2020-28949
Published: 19 November 2020
Summary
CVE-2020-28949 is a high-severity an unspecified weakness vulnerability in Fedoraproject Fedora. Its CVSS base score is 7.8 (High).
Operationally, ranked in the top 0.2% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 SI-10 (Information Input Validation) and AC-3 (Access Enforcement).
Deeper analysis
Archive_Tar through version 1.4.10 contains a filename sanitization flaw that only blocks phar:// stream wrappers to prevent certain attacks. The component is the PEAR Archive_Tar library used for tar archive handling in PHP applications. As a result, other stream wrappers such as file:// remain usable and can lead to arbitrary file operations during archive extraction.
An attacker can supply a specially crafted tar archive that, when processed by a vulnerable application, leverages alternate stream wrappers to overwrite arbitrary files on the local system. The attack requires local access and user interaction to open the archive but needs no prior privileges, enabling high-impact outcomes including confidentiality, integrity, and availability compromise as reflected in its CVSS 7.8 rating.
Advisories from Debian LTS and Fedora recommend updating Archive_Tar to a patched release that fully addresses stream-wrapper handling. Corresponding package updates are referenced in the Fedora and Debian mailing list announcements, along with a public proof-of-concept on Packet Storm.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-0783
Vulnerability details
Archive_Tar through 1.4.10 has :// filename sanitization only to address phar attacks, and thus any other stream-wrapper attack (such as file:// to overwrite files) can still succeed.
- CWE(s)
- KEV Date Added
- 25 August 2022
Related Threats
No named actor attribution yet. ATT&CK technique mapping in progress for this CVE.
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly requires validation and sanitization of untrusted filename input in Archive_Tar to block stream-wrapper sequences such as file://.
Enforces access-control decisions on file writes so that even a successful stream-wrapper attack cannot overwrite arbitrary system files without proper authorization.
Requires integrity verification of files and extracted content, enabling detection of unauthorized overwrites performed via the Archive_Tar flaw.