Secret key base exposed in stack trace arguments on wrong-typed Plug.Crypto arguments

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-105963
StatePUBLISHED
AssignerEEF
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-10-23 10:16:40 UTC
Updated2026-10-23 14:17:30 UTC
DescriptionExternally-Generated Error Message Containing Sensitive Information vulnerability in plug_crypto in elixir-plug plug_crypto allows an unauthenticated remote attacker to expose the secret key base through application logs via a wrong-typed argument. Every public function in Plug.Crypto validates argument types in a function-head guard. A failed guard makes the Erlang VM raise FunctionClauseError with the actual argument values in the top stack frame, so the secret key base, a derived key, or the value an API key is compared against lands in that frame. The library's rescue blocks and Plug.Crypto.prune_args_from_stacktrace/1 only reach exceptions raised inside a function body, so they never see a guard failure. Plug.Cowboy and Bandit write the frame to the error log and attach it as crash_reason Logger metadata, which error trackers forward. Two entry points take request data. Plug.Crypto.verify/4 exposes the secret key base when the token is neither a binary nor nil, which Phoenix.Token.verify/4 reaches because it forwards the token unguarded. Plug.Crypto.secure_compare/2 exposes the other operand when one side is not a binary, as happens when a missing request header yields nil. Reading the leaked value needs separate access to the logs or the error tracker, so the request alone does not disclose the secret to the attacker. This issue affects plug: from 1.6.3 before 1.7.0; plug_crypto: from 1.0.0 before 2.2.1.

Risk And Classification

Primary CVSS: v4.0 5.1 MEDIUM from 6b3ad84c-e1a6-4bf7-a703-f496b71e49db

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-532 | CWE-532 CWE-532 Insertion of Sensitive Information into Log File

VersionSourceTypeScoreSeverityVector
4.06b3ad84c-e1a6-4bf7-a703-f496b71e49dbSecondary5.1MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/C...
4.0CNACVSS5.1MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
High
User Interaction
None
Confidentiality
Low
Integrity
None
Availability
None
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Elixir-plug Plug affected 1.6.3 1.7.0 semver Not specified
CNA Elixir-plug Plug affected 56000c33d8a0a2fbac491f8be06b9c5112bc2276 * git Not specified
CNA Elixir-plug Plug Crypto affected 1.0.0 2.2.1 semver Not specified
CNA Elixir-plug Plug Crypto affected 2d078b7b8264c565f0ff71235c515f4f46882dcf 981887493dada0fce7003c61861c00dfbb0fc8c5 git Not specified

References

ReferenceSourceLinkTags
github.com/elixir-plug/plug/security/advisories/GHSA-ffw9-w85g-f2vh 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
osv.dev/vulnerability/EEF-CVE-2026-105963 6b3ad84c-e1a6-4bf7-a703-f496b71e49db osv.dev
cna.erlef.org/cves/CVE-2026-105963.html 6b3ad84c-e1a6-4bf7-a703-f496b71e49db cna.erlef.org
github.com/elixir-plug/plug/commit/aeaa90e76b73ea90c3ecca9aae16fce71bd2a8d4 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
github.com/elixir-plug/plug_crypto/commit/2d078b7b8264c565f0ff71235c515f... 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
github.com/elixir-plug/plug_crypto/commit/981887493dada0fce7003c61861c00... 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
github.com/elixir-plug/plug/commit/56000c33d8a0a2fbac491f8be06b9c5112bc2276 6b3ad84c-e1a6-4bf7-a703-f496b71e49db github.com
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Neil Berkman (en)

CNA: Neil Berkman (en)

CNA: Neil Berkman (en)

CNA: Jonatan Männchen / EEF (en)

CNA: José Valim (en)

Additional Advisory Data

Workarounds

CNA: Check argument types in the calling code before entering Plug.Crypto, so no head guard ever fails. Pass a token to Phoenix.Token.verify/4, Phoenix.Token.decrypt/4, Plug.Crypto.verify/4 or Plug.Crypto.decrypt/4 only when is_binary(token) holds, and treat anything else as an invalid token. Call Plug.Crypto.secure_compare/2 only when both operands are binaries, treating a missing header or parameter as a failed comparison rather than passing nil. Where the leaked value matters more than the crash, configuring the error tracker to drop stack-frame arguments also keeps the secret out of the forwarded report. For Sentry this means not sending vars with the crash report. This narrows exposure but leaves the value in the local error log.

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