phpseclib/phpseclib security advisory

CVE-2026-44167: Phpseclib has a CVE-2024-27355 mitigation bypass — OID amplification DoS in ASN1::decodeOID()

CVE-2026-44167 is a high-severity denial of service vulnerability in the PHP package phpseclib/phpseclib (CVSS 7.5), published 12 May 2026. The advisory does not name a fixed version. It can be exploited without an account.

high 7.5 published 2026-05-12 · updated 2026-06-17

Affected versions: >= 0.1.1, <= 1.0.28
>= 2.0.0, <= 2.0.53
>= 3.0.0, <= 3.0.51
Fixed in: not stated
Newest release: 4.0.3
Severity: High · CVSS 7.5
Type: Denial of service
CWE-400
Exploited in the wild: Not on the CISA KEV list
checked 2026-11-04

Is your phpseclib/phpseclib version affected?

Run composer show phpseclib/phpseclib in your project, then enter the version. We check it against this and every other known phpseclib/phpseclib advisory.

Who can exploit CVE-2026-44167

Access: No account. Anyone who can send a request to an app that uses the affected code.

CVSS vector (scored by GitHub): CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Your app is only exposed if it uses the affected part of phpseclib/phpseclib. The advisory below says which part that is. If you are not sure, upgrade anyway: it costs less than finding out.

How to fix CVE-2026-44167 in phpseclib/phpseclib

Find the installed version: composer show phpseclib/phpseclib. If you never required it yourself, composer why phpseclib/phpseclib shows which package pulls it in.
Update it: composer update phpseclib/phpseclib --with-all-dependencies.
If Composer will not go that high, your composer.json constraint is holding it back. Widen it (for example "phpseclib/phpseclib": "^4.0.3" if you can take that version), or upgrade the package that requires it.
Run composer audit. It reads the same advisory data and should no longer list CVE-2026-44167.
Commit composer.lock and deploy it. On the server, run composer install --no-dev from the lock file, not composer update.

If you cannot upgrade yet

General hardening for denial of service issues while the upgrade waits. None of it replaces the fix.

Rate-limit the affected endpoint and cap request body, header and upload sizes at the web server.
If your app does not use the affected feature, note that in your audit, but still plan the upgrade.

The CVE-2026-44167 advisory

phpseclib is a PHP secure communications library. Prior to 1.0.29, 2.0.54, and 3.0.52, anyone loading untrusted ASN1 files (eg. X509 certificates, RSA PKCS8 private or public keys, etc). This is a bypass of CVE-2024-27355. This vulnerability is fixed in 1.0.29, 2.0.54, and 3.0.52.

Description from the CVE record, published by GitHub (the CVE Numbering Authority), via the NVD entry for CVE-2026-44167. Advisory title: “phpseclib has a CVE-2024-27355 mitigation bypass — OID amplification DoS in ASN1::decodeOID()”.

References

GitHub advisory GHSA-3qpq-r242-jqj7 github.com
Fix commit d53d202 github.com

Other phpseclib/phpseclib advisories

medium CVE-2026-84308: Phpseclib — non-constant-time X25519 scalar multiplication permits full private-key recovery 2026-09-08
medium CVE-2026-55599: Phpseclib: X.509 certificate validation sends attacker-controlled outbound requests (server-side request forgery) via Authority… 2026-06-16
low CVE-2026-40194: Phpseclib has a variable-time HMAC comparison in SSH2::get_binary_packet() using != instead of hash_equals() 2026-04-10
high CVE-2026-32935: Phpseclib's AES-CBC unpadding susceptible to padding oracle timing attack 2026-03-19
high CVE-2023-52892: Name confusion in x509 Subject Alternative Name fields 2024-06-28
high CVE-2024-27354: Phpseclib a large prime can cause a denial of service 2024-03-02

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Where this data comes from

Affected and fixed versions: the Packagist security advisories API (GitHub Advisory Database and FriendsOfPHP), the same data composer audit uses. Synced 2026-11-03.
Description, score, weakness and references: NIST National Vulnerability Database (NVD), checked 2026-11-04. This product uses data from the NVD API but is not endorsed or certified by the NVD.
Exploited-in-the-wild status: the CISA Known Exploited Vulnerabilities catalog, checked 2026-11-04.
Compiled by Daniel Lasek at Laskyr from the sources above. The summary, “who can exploit it”, “how to fix it” and hardening sections are our plain-English reading of the record and are generated from it. The quoted description is the record's own text. Spot an error? Tell us.