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CVE-2026-84308

CVE-2026-84308 · phpseclib — non-constant-time X25519 scalar multiplication permits full private-key recovery

This page contains facts from public vulnerability sources. Check the original advisory before updating.

This page shows selected source facts. See the linked advisories for the complete description and affected versions.

phpseclib is a PHP secure communications library. Prior to 3.0.57 and 4.0.1, pure-PHP X25519 scalar multiplication in phpseclib/Math/PrimeField/Integer.php performs data-dependent conditional modular reductions in add() and subtract(). During the Montgomery ladder in phpseclib/Crypt/EC/BaseCurves/Montgomery.php, the reduction behavior of each step depends on the secret scalar prefix, creating per-step timing and libgmp call-count observations that can reveal a reused 251-bit clamped private scalar. The phpseclib/Crypt/EC/Formats/Keys/MontgomeryPrivate.php derivation path invokes the pure-PHP multiplication without a native-engine check, while phpseclib/Crypt/EC/Formats/Keys/PKCS8.php reaches it when ext-sodium is unavailable. Exploitation requires a reused or long-lived X25519 private key, knowledge of the corresponding public key, execution of the pure-PHP path, and a local observer capable of resolving individual ladder steps or libgmp entry-point calls. Ephemeral X25519 keys, including phpseclib's normal SSH exchange path, are not affected. Recovery of the scalar permanently compromises operations that reuse that key. This issue is fixed in versions 3.0.57 and 4.0.1.

CVSS 6.3 · Medium · EPSS 0.3% · Fix available

Published
Updated

Stack: system · php

Affected products and versions

  • phpseclib

    Versions
    • < 3.0.57: Affected
    • >= 4.0.0, < 4.0.1: Affected

    No fix published

  • php-phpseclib3 Debian:12

    Versions
    • 3.0.19-1
    • 3.0.19-1+deb12u1
    • 3.0.19-1+deb12u2
    • 3.0.19-1+deb12u3
    • 3.0.19-1+deb12u4
    • 3.0.19-1+deb12u6
    • 3.0.20-1
    • 3.0.21-1
    • 3.0.21-2
    • 3.0.22-1
    • 3.0.23-1
    • 3.0.33-1
    • 3.0.34-1
    • 3.0.35-1
    • 3.0.36-1
    • 3.0.37-1
    • 3.0.38-1
    • 3.0.39-1
    • 3.0.41-1
    • 3.0.42-1
    • 3.0.43-1
    • 3.0.43-2
    • 3.0.44-1
    • 3.0.44-2
    • 3.0.45-1
    • 3.0.46-1
    • 3.0.46-2
    • 3.0.47-1
    • 3.0.48-1
    • 3.0.49-1
    • 3.0.50-1
    • 3.0.51-1
    • 3.0.52-1
    • 3.0.52-2
    • 3.0.53-1
    • 3.0.55-1
    • 3.0.56-1
    • 3.0.57-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib3 Debian:13

    Versions
    • 3.0.43-2
    • 3.0.43-2+deb13u1
    • 3.0.43-2+deb13u3
    • 3.0.44-1
    • 3.0.44-2
    • 3.0.45-1
    • 3.0.46-1
    • 3.0.46-2
    • 3.0.47-1
    • 3.0.48-1
    • 3.0.49-1
    • 3.0.50-1
    • 3.0.51-1
    • 3.0.52-1
    • 3.0.52-2
    • 3.0.53-1
    • 3.0.55-1
    • 3.0.56-1
    • 3.0.57-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib3 Debian:14

    Versions
    • 3.0.43-2
    • 3.0.44-1
    • 3.0.44-2
    • 3.0.45-1
    • 3.0.46-1
    • 3.0.46-2
    • 3.0.47-1
    • 3.0.48-1
    • 3.0.49-1
    • 3.0.50-1
    • 3.0.51-1
    • 3.0.52-1
    • 3.0.52-2
    • 3.0.53-1
    • 3.0.55-1
    • 3.0.56-1
    Affected ranges
    • ECOSYSTEM: < 3.0.57-1

    Update to 3.0.57-1

  • php-phpseclib4 Debian:14

    Versions
    • 4.0.0-1
    Affected ranges
    • ECOSYSTEM: < 4.0.1-1

    Update to 4.0.1-1

  • phpseclib/phpseclib Packagist

    Versions
    • 0.3.0
    • 0.3.1
    • 0.3.10
    • 0.3.5
    • 0.3.6
    • 0.3.7
    • 0.3.8
    • 0.3.9
    • 1.0.0
    • 1.0.1
    • 1.0.10
    • 1.0.11
    • 1.0.12
    • 1.0.13
    • 1.0.14
    • 1.0.15
    • 1.0.16
    • 1.0.17
    • 1.0.18
    • 1.0.19
    • 1.0.2
    • 1.0.20
    • 1.0.21
    • 1.0.22
    • 1.0.23
    • 1.0.24
    • 1.0.25
    • 1.0.26
    • 1.0.27
    • 1.0.28
    • 1.0.29
    • 1.0.3
    • 1.0.30
    • 1.0.4
    • 1.0.5
    • 1.0.6
    • 1.0.7
    • 1.0.8
    • 1.0.9
    • 2.0.0
    • 2.0.1
    • 2.0.10
    • 2.0.11
    • 2.0.12
    • 2.0.13
    • 2.0.14
    • 2.0.15
    • 2.0.16
    • 2.0.17
    • 2.0.18
    • 2.0.19
    • 2.0.2
    • 2.0.20
    • 2.0.21
    • 2.0.22
    • 2.0.23
    • 2.0.24
    • 2.0.25
    • 2.0.26
    • 2.0.27
    • 2.0.28
    • 2.0.29
    • 2.0.3
    • 2.0.30
    • 2.0.31
    • 2.0.32
    • 2.0.33
    • 2.0.34
    • 2.0.35
    • 2.0.36
    • 2.0.37
    • 2.0.38
    • 2.0.39
    • 2.0.4
    • 2.0.40
    • 2.0.41
    • 2.0.42
    • 2.0.43
    • 2.0.44
    • 2.0.45
    • 2.0.46
    • 2.0.47
    • 2.0.48
    • 2.0.49
    • 2.0.5
    • 2.0.50
    • 2.0.51
    • 2.0.52
    • 2.0.53
    • 2.0.54
    • 2.0.55
    • 2.0.6
    • 2.0.7
    • 2.0.8
    • 2.0.9
    • 3.0.0
    • 3.0.1
    • 3.0.10
    • 3.0.11
    • 3.0.12
    • 3.0.13
    • 3.0.14
    • 3.0.15
    • 3.0.16
    • 3.0.17
    • 3.0.18
    • 3.0.19
    • 3.0.2
    • 3.0.20
    • 3.0.21
    • 3.0.22
    • 3.0.23
    • 3.0.3
    • 3.0.33
    • 3.0.34
    • 3.0.35
    • 3.0.36
    • 3.0.37
    • 3.0.38
    • 3.0.39
    • 3.0.4
    • 3.0.40
    • 3.0.41
    • 3.0.42
    • 3.0.43
    • 3.0.44
    • 3.0.45
    • 3.0.46
    • 3.0.47
    • 3.0.48
    • 3.0.49
    • 3.0.5
    • 3.0.50
    • 3.0.51
    • 3.0.52
    • 3.0.53
    • 3.0.54
    • 3.0.55
    • 3.0.56
    • 3.0.6
    • 3.0.7
    • 3.0.8
    • 3.0.9
    Affected ranges
    • ECOSYSTEM: < 3.0.57

    Update to 3.0.57

  • phpseclib/phpseclib Packagist

    Versions
    • 4.0.0
    Affected ranges
    • ECOSYSTEM: ≥ 4.0.0, < 4.0.1

    Update to 4.0.1

  • php-phpseclib Ubuntu:Pro:16.04:LTS

    Versions
    • 2.0.1-1
    • 2.0.1-1build1
    • 2.0.1-1ubuntu0.1~esm1
    • 2.0.1-1ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • phpseclib Ubuntu:Pro:16.04:LTS

    Versions
    • 0.3.10-3
    • 1.0.0-2
    • 1.0.0-3
    • 1.0.1-1
    • 1.0.1-3
    • 1.0.1-3ubuntu0.1
    • 1.0.1-3ubuntu0.1+esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib Ubuntu:Pro:18.04:LTS

    Versions
    • 2.0.6-1
    • 2.0.7-1
    • 2.0.9-1
    • 2.0.9-1ubuntu0.1~esm2
    • 2.0.9-1ubuntu0.1~esm3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • phpseclib Ubuntu:Pro:18.04:LTS

    Versions
    • 1.0.7-1
    • 1.0.8-1
    • 1.0.9-1
    • 1.0.9-1ubuntu0.1~esm1
    • 1.0.9-1ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib Ubuntu:Pro:20.04:LTS

    Versions
    • 2.0.21-2
    • 2.0.23-2
    • 2.0.23-2ubuntu0.1~esm2
    • 2.0.23-2ubuntu0.1~esm3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • phpseclib Ubuntu:Pro:20.04:LTS

    Versions
    • 1.0.16-2
    • 1.0.18-2
    • 1.0.18-2ubuntu0.1~esm1
    • 1.0.18-2ubuntu0.1~esm2
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib Ubuntu:Pro:22.04:LTS

    Versions
    • 2.0.30-2ubuntu1
    • 2.0.34-1
    • 2.0.35-1
    • 2.0.36-1
    • 2.0.36-1ubuntu0.1~esm2
    • 2.0.36-1ubuntu0.1~esm3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib3 Ubuntu:Pro:22.04:LTS

    Versions
    • 3.0.9-1
    • 3.0.10-1
    • 3.0.12-2
    • 3.0.13-1
    • 3.0.13-1ubuntu0.1~esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • phpseclib Ubuntu:22.04:LTS

    Versions
    • 1.0.19-3ubuntu2
    • 1.0.19-3ubuntu3
    • 1.0.20-1
    • 1.0.20-1ubuntu0.1~esm1
    • 1.0.20-1+deb12u3build0.22.04.1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib3 Ubuntu:24.04:LTS

    Versions
    • 3.0.21-2
    • 3.0.33-1
    • 3.0.34-1
    • 3.0.35-1
    • 3.0.37-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib Ubuntu:Pro:24.04:LTS

    Versions
    • 2.0.44-1
    • 2.0.45-1
    • 2.0.46-1
    • 2.0.47-1
    • 2.0.47-1ubuntu0.1~esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • phpseclib Ubuntu:Pro:24.04:LTS

    Versions
    • 1.0.21-2
    • 1.0.22-1
    • 1.0.23-1
    • 1.0.23-1ubuntu0.1~esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib Ubuntu:26.10

    Versions
    • 2.0.51-1
    • 2.0.54-1
    • 2.0.55-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib3 Ubuntu:26.10

    Versions
    • 3.0.49-1ubuntu1
    • 3.0.57-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • phpseclib Ubuntu:26.10

    Versions
    • 1.0.24-1
    • 1.0.29-1
    • 1.0.30-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib3 Ubuntu:26.04:LTS

    Versions
    • 3.0.43-2
    • 3.0.44-1
    • 3.0.47-1
    • 3.0.49-1
    • 3.0.49-1ubuntu1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • php-phpseclib Ubuntu:Pro:26.04:LTS

    Versions
    • 2.0.48-3
    • 2.0.49-1
    • 2.0.51-1
    • 2.0.51-1ubuntu0.1~esm1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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