GHSA-q97c-8qh3-fpc6: phpseclib/phpseclib (CVE-2026-84308)

Package	Ecosystem	Affected	Fixed in
phpseclib/phpseclib	Packagist	<3.0.57 \|\| >=4.0.0, <4.0.1	3.0.57, 4.0.1

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

phpseclib before 3.0.57, and 4.0.0 before 4.0.1, uses a non-constant-time pure-PHP X25519 scalar multiplication whose per-step timing depends on the secret scalar. An attacker who can observe per-step timing or GMP library call counts on the same host, and who knows the victim's public key, can recover a reused long-lived X25519 private key; this was shown in an instrumented model and only applies when the pure-PHP path runs. Upgrade to 3.0.57 or 4.0.1.

Written 31 Oct 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
6.3	Medium	3.1	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N	CNA (GitHub_M)

CISA KEV Not listed.
EPSS 0.0033, the 25th percentile, on 5 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

31 Oct 2026, 13:54 UTC First seen by agentprime
31 Oct 2026, 13:54 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.