CISA adds Looney Tunables Linux bug to its Known Exploited Vulnerabilities catalog
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2017-9841 | Unauthenticated Remote Code Execution in PHPUnit eval-stdin.php PHPUnit ships a utility script (eval-stdin.php under /vendor/phpunit/phpunit/src/Util/PHP/) that reads HTTP POST data and evaluates it as PHP code with no authentication. The flaw is triggered when a site's /vendor folder is web-accessible and an attacker sends a POST request whose body begins with '<?php ' directly to that URI. Doing so lets the attacker execute arbitrary PHP code on the server under the web server account, giving unauthenticated remote code execution (CWE-94 code injection). Anyone running a PHP application installed with Composer, where PHPUnit is present in the vendor tree and that directory is reachable over HTTP, is affected. The flaw is under active exploitation: CISA added it to the Known Exploited Vulnerabilities catalog on 2022-02-15 and its EPSS probability of exploitation is 100% (top percentile). Do: Apply the CISA KEV required action by updating PHPUnit per vendor instructions, which in practice means updating the CMS/framework or running a Composer update that pulls a patched PHPUnit release. Until patched, block web access to the /vendor directory (e.g., deny /vendor/ or at least /vendor/phpunit/phpunit/src/Util/PHP/eval-stdin.php in your web server configuration) and verify the endpoint is no longer reachable. Check access logs for POST requests to eval-stdin.php and investigate affected servers for webshells or other signs of compromise. | 9.8 | 100% | KEV |
| masshundreds of thousands of PHP sites/servers potentially exposed (order-of-magnitude estimate; unknown precise count) | |
| CVE-2023-4911 | Buffer Overflow in GNU C Library ld.so Grants Root via SUID Binaries CVE-2023-4911 ('Looney Tunables') is a buffer overflow in the GNU C Library's dynamic loader (ld.so) that occurs while processing the GLIBC_TUNABLES environment variable. A local attacker triggers it by launching a set-user-ID (SUID) binary with a maliciously crafted GLIBC_TUNABLES value, corrupting memory in the privileged process. This allows the attacker to execute code with elevated (root) privileges on the host. Any system running an affected glibc is potentially exposed, including major Linux distributions (Fedora, Red Hat, Canonical, Debian), Red Hat CodeReady Linux Builder channels, NetApp products, and Siemens SIMATIC S7-1500 firmware, although exploitation requires local execution capability or a foothold on the machine. Exploitation is confirmed in the wild: Qualys published a working proof-of-concept, the flaw was added to CISA's Known Exploited Vulnerabilities catalog on 2023-11-21, and Kinsing threat actors have used it for cryptojacking and to breach cloud environments. Do: Install patched glibc updates from your distribution vendor (Fedora, Red Hat, Canonical/Ubuntu, Debian) and apply Siemens firmware updates for affected SIMATIC S7-1500 MFP devices; NetApp customers should follow NetApp's remediation guidance. Until patched, audit SUID/SGID binaries (which the attacker needs as the escalation trigger) and limit untrusted local access and shell access on multi-user or cloud-hosted Linux systems. Per the CISA KEV required action, apply vendor mitigations or discontinue use, prioritizing internet-facing hosts given active Kinsing cryptojacking and cloud-breach activity. | 7.8 | 81% | KEV PoC ×6 |
| masshundreds of millions of Linux installations worldwide (glibc is the standard C library shipped with virtually every major distribution) |
Full article523 words · extracted from securityaffairs.com · click to collapse
Pierluigi Paganini
November 22, 2023
US CISA adds Looney Tunables Linux flaw to its Known Exploited Vulnerabilities catalog.
The U.S. Cybersecurity and Infrastructure Security Agency (CISA) added Looney Tunables Linux vulnerability to its Known Exploited Vulnerabilities (KEV) catalog.
The vulnerability CVE-2023-4911 (CVSS score 7.8), aka Looney Tunables, is a buffer overflow issue that resides in the GNU C Library’s dynamic loader ld.so while processing the GLIBC_TUNABLES environment variable. An attacker can trigger the vulnerability to execute code with elevated privileges.
“A buffer overflow was discovered in the GNU C Library’s dynamic loader ld.so while processing the GLIBC_TUNABLES environment variable. This issue could allow a local attacker to use maliciously crafted GLIBC_TUNABLES environment variables when launching binaries with SUID permission to execute code with elevated privileges.” reads the advisory.
Researchers at Qualys’ Threat Research Unit disclosed the vulnerability, also named Looney Tunables, last week and published a PoC exploit.
The buffer overflow affects multiple Linux distros, including Debian, Fedora, and Ubuntu.
The researchers highlighted the widespread nature of this vulnerability.
“We have successfully identified and exploited this vulnerability (a local privilege escalation that grants full root privileges) on the default installations of Fedora 37 and 38, Ubuntu 22.04 and 23.04, and Debian 12 and 13.” reads the post published by Qualys. “It’s likely that other distributions are similarly susceptible, although we’ve noted that Alpine Linux remains an exception due to its use of musl libc instead of glibc. This vulnerability was introduced in April 2021.”
Multiple security researchers have already developed their own proof-of-concept exploits for this flaw.
According to Binding Operational Directive (BOD) 22-01: Reducing the Significant Risk of Known Exploited Vulnerabilities, FCEB agencies have to address the identified vulnerabilities by the due date to protect their networks against attacks exploiting the flaws in the catalog.
Experts recommend also private organizations review the Catalog and address the vulnerabilities in their infrastructure.
CISA orders federal agencies to fix these vulnerabilities by December 12, 2023.
Researchers from Aqua Nautilus spotted experimental incursions into cloud environments by Kinsing actors. The attackers used a rudimentary yet PHPUnit vulnerability exploit, they attempted to manipulate the Looney Tunables vulnerability (CVE-2023-4911). The experts pointed out that this marks the first documented instance of such an exploit.
“This marks the first documented instance of such an exploit, to the best of our knowledge.” reads the analysis published by Aqua firm. “Intriguingly, the attacker is also broadening the horizons of their cloud-native attacks by extracting credentials from the Cloud Service Provider (CSP).”
The discovery demonstrates that Kinsing actors are rapidly adding new exploits to their arsenal, expanding the potential targets. Recently, observers noticed Kinsing actors exploiting vulnerable Openfire servers.
Kinsing actors often exploited the PHPUnit vulnerability (CVE-2017-9841) and it engaged in fully automated attacks as part of mining cryptocurrency. With the recent discovery, the experts observed Kinsing conducting manual tests, which marks a deviation from their usual modus operandi.
Experts noted the attackers using a Python-based Linux local privilege escalation exploit published by the researcher bl4sty
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