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[USN-8830-1] phpseclib vulnerabilities

Posted on 29 September 2026
Ubuntu Security

==========================================================================Ubuntu Security Notice USN-8830-1
September 28, 2026

php-phpseclib vulnerabilities
==========================================================================
A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 26.04 LTS
- Ubuntu 24.04 LTS
- Ubuntu 22.04 LTS
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in phpseclib.

Software Description:
- php-phpseclib: implementations of an arbitrary-precision integer arithmetic library

Details:

It was discovered that phpseclib did not perform constant-time padding
validation when using AES in CBC mode. A remote attacker could possibly
use this issue to obtain sensitive information. (CVE-2026-32935)

It was discovered that phpseclib did not use a constant-time comparison
when validating SSH packet authentication codes. A remote attacker could
possibly use this issue to obtain sensitive information. (CVE-2026-40194)

It was discovered that phpseclib did not properly limit object identifier
lengths when parsing ASN.1 data. An attacker could possibly use this issue
to cause phpseclib to use excessive resources, leading to a denial of
service. (CVE-2026-44167)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 26.04 LTS
php-phpseclib 2.0.51-1ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 24.04 LTS
php-phpseclib 2.0.47-1ubuntu0.1~esm1
Available with Ubuntu Pro

Ubuntu 22.04 LTS
php-phpseclib 2.0.36-1ubuntu0.1~esm3
Available with Ubuntu Pro

Ubuntu 20.04 LTS
php-phpseclib 2.0.23-2ubuntu0.1~esm3
Available with Ubuntu Pro

Ubuntu 18.04 LTS
php-phpseclib 2.0.9-1ubuntu0.1~esm3
Available with Ubuntu Pro

Ubuntu 16.04 LTS
php-phpseclib 2.0.1-1ubuntu0.1~esm1
Available with Ubuntu Pro

In general, a standard system update will make all the necessary changes.

References:
https://ubuntu.com/security/notices/USN-8830-1
CVE-2026-32935, CVE-2026-40194, CVE-2026-44167

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