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CVE-2020-36193PEAR Archive_Tar Improper Link Resolution Vulnerability

Patch nowHigh7.5Exploited, CISA due date 2022-09-15EPSS 71%, higher than 99% of scored CVEs

CVE-2020-36193 is a path traversal in PEAR Archive_Tar, rated high (7.5 on CVSS 3.1).

Why this priority: Exploited in the wild: listed in CISA's KEV catalog.

Published · Updated · NVD status: Analyzed

What it is

A file name from the request can climb out of the intended folder with sequences like ../, reaching files the service never meant to expose. The software follows a symbolic link an attacker planted, so it reads or writes a file other than the one it checked.

How it is reached

An attacker can exploit it over the network, without an account, and nobody has to click anything.

What an attacker gains

A successful attack can change data or behaviour. In practice, this kind of flaw lets an attacker read or write files outside the folders the service meant to expose.

Is it being exploited?

CISA added it to the Known Exploited Vulnerabilities catalog on 2022-08-25: it is being exploited in the wild. It can be exploited automatically, at scale. EPSS estimates a 71% chance of exploitation activity in the next 30 days, higher than 99% of scored CVEs.

What to do

  1. Treat it as urgent: it is on CISA's KEV list. CISA's deadline for US federal agencies: 2022-09-15.
  2. No fixed version is listed for PEAR Archive_Tar itself; fixed versions for the other affected products are listed on this page.
  3. Until it is patched, keep it off the internet or behind a VPN, allowlist or authenticating proxy.
  4. Check exposed instances for signs of compromise, not only for the version.

Description from NVD

Tar.php in Archive_Tar through 1.4.11 allows write operations with Directory Traversal due to inadequate checking of symbolic links, a related issue to CVE-2020-28948.

What this means for your architecture.

A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.

Components it touches

  • Operating systems on servers, workstations or devices. Everything on the host inherits the flaw.
  • File storage the service can read or write. The flaw sits between the application and the file system it can reach.

Trust boundaries in play

  • Internet-facing entry points. No account is needed. Any instance reachable from outside your perimeter, through a load balancer, gateway, VPN or exposed admin port, is in scope.
  • Between the application and the file system it can reach. An attacker who crosses it can read or write files outside the folders the service meant to expose.

Questions to answer about your own systems

  • Where does PEAR Archive_Tar run in your systems, and at which version?
  • Which of those instances can be reached from the internet or partner networks?
  • What can it reach once compromised: which data stores, secrets and services?
See how Veriom maps an architectureTake the interactive tour

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Sources

  • CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
  • Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
  • Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
  • Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.