> CVE-2026-84308 [MEDIUM]

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PUBLISHED
2026-09-01 20:17
MODIFIED
2026-09-01 20:17
CVSS_SCORE V3
6.3
EPSS (Prob. Exploit)
0.33%
Top 75.4%
DATA SOURCES:
NVD đź”— 2026-09-01 CWE MITRE đź”— 2026-10-01 FIRST EPSS đź”— 2026-10-25 GITHUB đź”— 2026-10-29 OSV đź”— 2026-09-06

> DESCRIPTION

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.

> AFFECTED_PRODUCTS

ℹ️ Aucun produit affecté n'a encore été publié par NVD pour cette CVE.

> CVSS V3 METRICS

CVSS_VECTOR
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
EXPLOITABILITY
1.0
IMPACT
5.2

> MÉTRIQUES CVSS DÉTAILLÉES

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
Métrique Valeur Interprétation
AV (Vecteur d'Attaque)
Attack Vector
Local (L)
Exploit nécessite un accès local au système
AC (Complexité d'Attaque)
Attack Complexity
High (H)
Conditions spécifiques doivent être réunies pour exploiter
PR (Privilèges Requis)
Privileges Required
Low (L)
Authentifié avec compte utilisateur basique
UI (Interaction Utilisateur)
User Interaction
None (N)
Aucune interaction utilisateur nécessaire
S (Périmètre)
Scope
Unchanged (U)
Impact reste dans le périmètre du composant compromis
C (Impact Confidentialité)
Confidentiality Impact
High (H)
Divulgation totale d'informations
I (Impact Intégrité)
Integrity Impact
High (H)
Modification totale des données possible
A (Impact Disponibilité)
Availability Impact
None (N)
Aucune interruption de service

> RÉSUMÉ DES IMPACTS

Confidentialité
High
Divulgation totale d'informations
Intégrité
High
Modification totale des données possible
Disponibilité
None
Aucune interruption de service

> WEAKNESSES

CWE-208 CWE-385

> CWE DETAILED DESCRIPTIONS

CWE-208: Observable Timing Discrepancy - Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not. | CWE-385: Covert Timing Channel - Covert timing channels convey information by modulating some aspect of system behavior over time, so that the program receiving the information can observe system behavior and infer protected information.

> GITHUB SECURITY ADVISORY

GHSA-q97c-8qh3-fpc6 MODERATE

phpseclib — non-constant-time X25519 scalar multiplication permits full private-key recovery

AFFECTED PACKAGES:
COMPOSER / phpseclib/phpseclib
>= 4.0.0, < 4.0.1
Fixed in: 4.0.1
COMPOSER / phpseclib/phpseclib
< 3.0.57
Fixed in: 3.0.57

> OSV (GOOGLE OPEN SOURCE VULNERABILITIES)

phpseclib — non-constant-time X25519 scalar multiplication permits full private-key recovery

AFFECTED PACKAGES:
Unknown / Unknown
58 versions affected
ALIASES:
GHSA-q97c-8qh3-fpc6

> HISTORIQUE DES MODIFICATIONS

Première apparition
01/09/2026 20:17
Source: NVD
đź“Š ENRICHISSEMENT 01/10/2026 06:01
CWE
Champ modifié: Description CWE
Ancienne valeur:
N/A
Nouvelle valeur:
CWE-208: Observable Timing Discrepancy - Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant infor...
Total des modifications: 1 Dernière mise à jour: 4 weeks ago

> REFERENCES

https://github.com/phpseclib/phpseclib/commit/fb56bc5bb9009b54a6c26b31aeec8ed944...
https://github.com/phpseclib/phpseclib/releases/tag/3.0.57
https://github.com/phpseclib/phpseclib/releases/tag/4.0.1
https://github.com/phpseclib/phpseclib/security/advisories/GHSA-q97c-8qh3-fpc6
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