Allocation of Resources Without Limits or Throttling in phpseclib - #VU164362
Published: November 10, 2026
Vulnerability identifier: #VU164362
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-770
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a CPU-exhaustion denial of service and starve PHP workers.
The vulnerability exists due to missing upper bounds on password-based key derivation iteration counts in phpseclib when loading untrusted encrypted PKCS#8 keys, PKCS#12 containers, or CMS password-recipient structures with a password. A remote attacker can supply a crafted file with an ASN.1 iterationCount near PHP_INT_MAX to force excessive hashing before decryption, exhausting worker capacity even when the ciphertext is invalid.
Affected software
phpseclib
Remediation
Install security update from vendor's website.
phpseclib - addressed in versions 1.0.31, 2.0.56, 3.0.58, 4.0.3