Improper Verification of Cryptographic Signature in ueberauth guardian allows an unauthenticated attacker to revoke a victim's session with a forged token.

Guardian.revoke/3 in lib/guardian.ex decodes the supplied token with peek/1, which performs no signature verification (it only base64-decodes the JWT header and payload). The resulting unverified claims are forwarded directly to the configured token module's revoke callback and the implementation's onrevoke callback, a state-mutating sink. The sibling operations refresh/2 and exchange/4 both call decodeandverify first, so the signature is checked before anything acts on the claims; revoke/3 is the only state-mutating path that acts on claims without verifying the signature.

An attacker who knows or guesses a victim's identifying claim values (jti, sub) can forge a JWT carrying those claims, sign it with an arbitrary key, and submit it to any endpoint that funnels a caller-supplied token into Guardian.revoke/3 (the standard logout / session-revocation pattern). When the token module mutates state keyed by the claims (whitelist deletion or blacklist insertion, for example a GuardianDb-style store), the victim's legitimate session is evicted. This is an unauthenticated session-revocation denial of service; the attacker never needs the signing secret.

This issue affects guardian: from 1.0.0 before 2.4.1.

Allocation of Resources Without Limits or Throttling in ueberauth guardian allows denial of service via unbounded atom creation from attacker-influenced binary input.

Guardian.Plug.Keys derives connection and session namespace keys by passing arbitrary binaries to String.toatom/1. basekey/1 in lib/guardian/plug/keys.ex converts any binary into the atom :"guardian<input>", and the derived helpers claimskey/1, resourcekey/1, and tokenkey/1 create a second atom on top of that. keyfromother/1 likewise converts a regex-captured binary through String.toatom/1. The public specs advertise String.t() as a valid argument, so passing a string is documented usage, and higher-level entry points such as Guardian.Plug.currenttoken(conn, key: key) thread the caller-supplied key straight into these functions.

String.toatom/1 creates a brand-new atom for every previously unseen binary, atoms are never garbage collected, and the BEAM atom table is fixed at roughly 1,048,576 entries by default. An application that routes attacker-influenced data (a tenant identifier, header, or other request input) into a Guardian key therefore mints one permanent atom per distinct value. A modest stream of varied, unauthenticated input permanently consumes the atom table and crashes the BEAM node, taking down every application running on it.

This issue affects guardian: from 0.1.0 before 2.4.1.

Allocation of Resources Without Limits or Throttling vulnerability in ueberauth guardian (Guardian.Permissions module) allows a denial of service via BEAM atom-table exhaustion.

This vulnerability is associated with program file lib/guardian/permissions.ex and program routines 'Elixir.Guardian.Permissions':encodepermissions!/1, 'Elixir.Guardian.Permissions':encodepermissionsintoclaims!/2, 'Elixir.Guardian.Permissions':doencodepermissions!/2.

The Guardian.Permissions mixin installs a public encodepermissions!/1 function on every module that does use Guardian.Permissions. For each key of the supplied map, encodepermissions!/1 calls String.toatom(tostring(k)) before any validation runs. The integer-value clause of doencodepermissions!/2 then short-circuits straight to encoding without validating the key against the configured permission set, so a key with an integer value is interned as a fresh atom with no exception raised. Atoms are never garbage collected and the BEAM atom table is a fixed-size resource (default roughly 1,048,576 entries), so each unique attacker-chosen key permanently consumes one slot. An attacker who can influence a permission map that reaches encodepermissions!/1 (for example a permissions map read from a request body and passed into token issuance via encodepermissionsintoclaims!/2) can mint an unbounded number of atoms and exhaust the atom table, crashing the entire BEAM node and every service running on it. The sibling decodepermissions/1 is not affected because it skips keys absent from the configured permission set.

This issue affects guardian: from 2.0.0 before 2.4.1.

Allocation of Resources Without Limits or Throttling in ueberauth guardian allows denial of service via unbounded atom creation from attacker-controlled binary input.

Guardian.Permissions.AtomEncoding encodes permission scopes by passing arbitrary binaries to String.toatom/1. When encode/3 in lib/guardian/permissions/atomencoding.ex is called with a list, each binary entry is handled by the encodevalue/3 binary clause, which calls String.toatom(value) with no allow-list check. The permset argument (the application's small, finite set of legitimate permission names) is discarded, so any external string flows straight into atom creation. This encoder is selected with use Guardian.Permissions, encoding: Guardian.Permissions.AtomEncoding and reached through the imported encode/3 entry point.

String.toatom/1 creates a brand-new atom for every previously unseen binary, atoms are never garbage collected, and the BEAM atom table is fixed at roughly 1,048,576 entries by default. An application that funnels attacker-influenced permission scopes (from a request body, a JWT claim, or other external input) into encode/3 therefore mints one permanent atom per distinct value. A modest stream of varied, unauthenticated input permanently consumes the atom table and crashes the BEAM node with systemlimit, taking down every application running on it.

The default encoder is Guardian.Permissions.BitwiseEncoding, which is not affected.

This issue affects guardian: from 2.0.0 before 2.4.1.