CVE-2024-27354 phpseclib: guardrails needed on isPrime and randomPrime

What is CVE-2024-27354?

CVE-2024-27354 is a high-severity denial of service vulnerability in Debian Debian Linux, published on 1 Mar 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

An issue was discovered in phpseclib 1.x before 1.0.23, 2.x before 2.0.47, and 3.x before 3.0.36. An attacker can construct a malformed certificate containing an extremely large prime to cause a denial of service (CPU consumption for an isPrime primality check). NOTE: this issue was introduced when attempting to fix CVE-2023-27560.

Weakness: CWE-400

Which versions are affected by CVE-2024-27354?

6 open source packages ship an affected version, including phpseclib/phpseclib. It affects 2 products.

Products include Debian Debian Linux, Phpseclib Phpseclib.

How do I fix CVE-2024-27354?

Upgrade phpseclib/phpseclib to a fixed version for your release line: 1.0.23, 2.0.47 or 3.0.36.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2024-27354 being exploited?

There is no known exploitation of CVE-2024-27354 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as CLSA-2026-1783386122, DEBIAN-CVE-2024-27354, GHSA-2528-jw5q-ww88, UBUNTU-CVE-2024-27354.