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NVD / CVE Program· CNA EEF

CVE-2026-66883: Oidcc.Plug.Authorize user agent session binding inert due to case-sensitive header lookup

Noroxi assessment

Priority: Monitor (action score 25/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.36% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: Erlang Ecosystem Foundation oidcc_plug 0.5.0, f15e52c5750aaba701104b10ed96cfac063bd557.

Low priority for now. Upgrade to Erlang Ecosystem Foundation oidcc_plug 0.5.0, f15e52c5750aaba701104b10ed96cfac063bd557 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Improper Handling of Case Sensitivity vulnerability in Erlang Ecosystem Foundation oidcc_plug (Oidcc.Plug.Authorize module) renders the user agent session binding inert, removing a defense in depth control against replay of a stolen session. This vulnerability is associated with program files lib/oidcc/plug/authorize.ex and lib/oidcc/plug/authorization_callback.ex, and program routines Oidcc.Plug.Authorize.call/2 and Oidcc.Plug.AuthorizationCallback.call/2. Oidcc.Plug.Authorize.call/2 reads the initiating client's user agent with get_req_header(conn, "User-Agent"). Plug lowercases incoming header names, but get_req_header/2 matches the supplied key exactly and performs no normalization of its own, so the mixed-case lookup always returns an empty list and nil is written into the session. On the callback side, Oidcc.Plug.AuthorizationCallback treats a stored nil user agent as nothing to compare and returns :ok without inspecting the request. The two behaviours combine so that the check passes unconditionally on every request, including for deployments that explicitly opted in with check_useragent: true, and an authorization callback can be completed from a different user agent than the one that initiated the flow without detection. The check fails open silently, with no error and no log entry, so a deployment cannot tell the binding is absent. The impact is limited to defense in depth. The inert check does not by itself allow an attacker to complete an authorization flow; it removes one layer that would otherwise hinder use of a stolen or leaked session, such as an exfiltrated session cookie replayed from a different client. The CSRF/state, nonce, and PKCE checks are unaffected and continue to function. Deployments that never enabled check_useragent are not affected in practice, since they never expected the binding. The corresponding lookup in Oidcc.Plug.AuthorizationCallback correctly uses the lowercase key and is not affected. This issue affects oidcc_plug: from 0.1.0-alpha.3 before 0.5.0.

MediumCVSS 6.3 · v4.0—No exploit Fix available
Published
Aug 4, 2026
Updated
Oct 23, 2026
EPSS
0.3% · 30th percentile

Report tools

JSON

Action score

25

Monitor

Low priority for now.

CVSS
25 / 40 · 6.3 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
proof of concept
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · EEF
6.3
NVD has not scored this yet; the score shown is the CNA’s.

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • No public exploit code on record
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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (EEF). Independent of NVD's CPE analysis and usually ahead of it.

  • Erlang Ecosystem Foundation oidcc_plug

    • 0.1.0-alpha.3 and later · before 0.5.0affected · semver
    • 0a75fb139d8e2686d1b75e0d48962323d2181673 and later · before f15e52c5750aaba701104b10ed96cfac063bd557affected · git

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Hexoidcc_plugfrom 0.1.0-alpha.3 · before 0.5.00.5.0

Same product

erlang ecosystem foundation: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-66884Oidcc.Plug.AuthorizationCallback accepts callbacks with no authorize session or no state parameter, defeating CSRF protection
    8Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Erlang Ecosystem Foundation oidcc_plug0.5.0Vendor (CNA)
Erlang Ecosystem Foundation oidcc_plugf15e52c5750aaba701104b10ed96cfac063bd557Vendor (CNA)
Hex:oidcc_plug0.5.0Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
Integrity
Availability
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
X

Weakness class (CWE)

CWE-178 · Improper Handling of Case Sensitivity

CVSS vector

CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

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References

Show all references (3 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records