CVE-2026-76835 — CVSS 9.1 CRITICAL Severity | NVD Vulnerability Record

ANALYST: BIVASH KUMAR NAYAK (CHIEF SECURITY ARCHITECT) • PUBLISHED: Tuesday, 25 August 2026
CVE-2026-76835 — CVSS 9.1 CRITICAL Severity | NVD Vulnerability Record
■ Executive Risk Command Center
CVE ID
CVE-2026-76835
CVSS Score
9.1
CRITICAL
CISA KEV
Not Listed
Not present in the verified catalog snapshot; this does not prove absence of exploitation
Urgent exposure review? — YES — CVSS ≥ 9.0 (Critical)

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🔍 CVE-2026-40575, CVE-2026-76835  |  ⚠ CVSS 9.1  |  📅 August 24, 2026  |  📂 Vulnerabilities  |  🛡 CYBERDUDEBIVASH®
CVE VULNERABILITY ADVISORY · CRITICAL
CDB-CTI-2026-BC337A76BAC3 · Generated 2026-08-24T18:59:53.550706Z
Executive Summary

OAuth2 Proxy honours a client-supplied X-Forwarded-Uri header when deciding whether a request may skip authentication, because the guard added for CVE-2026-40575 is inert in the default reverse-proxy configuration. GetRequestURI in pkg/requests/util/util.go prefers that header over the real request URI whenever CanTrustForwardedHeaders returns true, and isAllowedPath in oauthproxy.go matches the skip_auth_routes and skip_auth_regex allow list against the resulting path. CanTrustForwardedHeaders in pkg/apis/middleware/scope.go grants that trust when the caller's address is in the trusted proxy set, and buildTrustedProxyNetSet falls back to defaultTrustedProxyIPs, which is 0.0.0.0/0 and ::/0, whenever reverse proxy mode is enabled without trusted_proxy_ip configured. Every client is therefore treated as a trusted proxy. An unauthenticated attacker can request a protected upstream path while setting X-Forwarded-Uri to a value matching an allow-listed route, so the skip-auth decision is made against the spoofed value while the upstream receives the protected path unchanged. CVSS Score: 9.1 CWE: CWE-290

Decision: Validate relevance and exposure using the cited source and internal evidence before treating this record as an incident, confirmed compromise, or customer-specific finding.

Threat Classification and Evidence Status
Intelligence family
CVE Vulnerability Advisory
Technical severity
CRITICAL
Exploitation
Not confirmed by available evidence; not in verified KEV snapshot
Patch/remediation
Availability not established in the source record — verify vendor guidance
Verified Facts
Source type: CVE Vulnerability Advisory
Source publication time: 2026-08-24T18:17:21.570000
CVE: CVE-2026-76835
CVSS base score: 9.1
CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CWE: CWE-290
KEV catalog check: Not present in the successfully retrieved catalog snapshot; this does not prove absence of exploitation.
Technical Analysis

Vulnerability class: Unclassified. Assessment: Active exploitation is not confirmed by the available evidence. This vulnerability is exploitable over the network, requiring no privileges and no user interaction. Prioritization must combine technical severity, exposure, asset criticality, and compensating controls.

Exposure and Remediation Decisions
P0 — Inventory: Confirm the affected product and version against authoritative vendor/NVD data; prioritize internet-facing and business-critical assets.
P0 — Remediation: Availability not established in the source record — verify vendor guidance
P1 — Compensating controls: Restrict exposure, enforce least privilege, and apply vendor-supported mitigations when immediate remediation is not possible.
P1 — Retrospective review: Search only the telemetry relevant to the affected component and validated vulnerability class; absence of alerts does not prove absence of exploitation.
Source Evidence Extract
CVE ID: CVE-2026-76835
Description: OAuth2 Proxy honours a client-supplied X-Forwarded-Uri header when deciding whether a request may skip authentication, because the guard added for CVE-2026-40575 is inert in the default reverse-proxy configuration. GetRequestURI in pkg/requests/util/util.go prefers that header over the real request URI whenever CanTrustForwardedHeaders returns true, and isAllowedPath in oauthproxy.go matches the skip_auth_routes and skip_auth_regex allow list against the resulting path. CanTrustForwardedHeaders in pkg/apis/middleware/scope.go grants that trust when the caller's address is in the trusted proxy set, and buildTrustedProxyNetSet falls back to defaultTrustedProxyIPs, which is 0.0.0.0/0 and ::/0, whenever reverse proxy mode is enabled without trusted_proxy_ip configured. Every client is therefore treated as a trusted proxy. An unauthenticated attacker can request a protected upstream path while setting X-Forwarded-Uri to a value matching an allow-listed route, so the skip-auth decision is made against the spoofed value while the upstream receives the protected path unchanged.
CVSS Score: 9.1
CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CWEs: CWE-290

This extract is escaped and rendered from the ingested source record; generated analysis is not presented as a source fact.

Detection Engineering
DETECTION STATUS: WITHHELD_INSUFFICIENT_EVIDENCE

The source record does not contain enough product-specific telemetry or observables for a defensible rule.

Confirm affected assets and versions, then collect the product's application, authentication, process, and network telemetry.
Use vendor-provided exploit indicators or a validated reproduction before publishing threat-specific detection logic.
References
AI-Native Automated Intelligence — Evidence-Graph Verified. Public reference draft — not a certified customer deliverable. Customer-specific action requires exposure validation and accountable human approval.
Role-Based Decisions
Vulnerability Manager: Track against cve vulnerability advisory intake. Exploitation status: Not confirmed by available evidence; not in verified KEV snapshot. Patch status: Availability not established in the source record — verify vendor guidance. — Prioritization reflects this record's own exploitation/patch evidence, not a fixed severity template.
Limitations: Reflects only this record's own reported exploitation and patch status; does not confirm whether the affected component is deployed in any specific environment.
SOC Manager: Review the detection guidance below before enabling any blocking action on it. — Detection maturity for this record is stated explicitly, not assumed production-ready.
Limitations: Detection guidance is evidence-scoped to this record; does not confirm the described technique has been observed in any specific environment.
Source Reliability & Corroboration

nvd

Source Reliability: B
Information Credibility: 3 (Possibly True)
Overall Analytical Confidence: MEDIUM

Reported by a single identified source; an independent second source has not been found (see the evidence ledger).

Threat Hunting — hunt-CDB-CTI-2026-BC337A76BAC3-exposure

Hypothesis: If CVE-2026-76835 is deployed and reachable as described by CDB-CTI-2026-BC337A76BAC3's evidence (CVE: CVE-2026-76835), telemetry consistent with the vulnerability class below may show attempted or successful exploitation.

Required telemetry: Confirm affected assets and versions, then collect the product's application, authentication, process, and network telemetry.
Required telemetry: Use vendor-provided exploit indicators or a validated reproduction before publishing threat-specific detection logic.
Pivot: Pivot on the affected component's inventoried version/build identifier, where available.
Pivot: Pivot on network paths and identities with reachability to the affected component.
Expected if true: Requests, processes, or events consistent with the vulnerability class described in this report's Technical Analysis, occurring after the CVE's public disclosure date and targeting the specific affected component.
Negative indicator: No matching telemetry for the affected component across the retrospective lookback window.
Negative indicator: The affected component is confirmed not deployed, or not reachable as this CVE describes.
False-positive risk: Legitimate administrative, diagnostic, or scanning activity against the same component can resemble exploitation attempts; corroborate with authentication context and known-good change records before escalating.

Success criteria: A specific, timestamped, corroborated telemetry match consistent with the vulnerability class, tied to the confirmed affected component.

Escalation criteria: Escalate to incident response only when a validated telemetry match is corroborated by at least one additional independent signal (e.g. an authentication anomaly or unexpected process lineage) -- a single matching log line alone is not sufficient grounds for escalation.

Confidence: MEDIUM — Maturity: PROPOSED (not independently confirmed by execution against real telemetry)

Limitations: Derived from the vulnerability class alone; does not confirm the affected component is actually deployed in the reader's environment, nor that matching telemetry represents genuine exploitation rather than benign activity.

Intelligence Gaps
Known Unknown: Whether an independent second source corroborates this record has not been assessed.
Would be resolved by: A second, independent source reporting the same underlying fact.
Indicators / Observables
CVE: CVE-2026-40575
CVE: CVE-2026-76835
Indicators are defanged for safe display (e.g. hxxp:// / [.]) -- refang before use in blocking or detection tooling.

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Contact: bivash@cyberdudebivash.com · Website: https://cyberdudebivash.com
Intelligence source: https://nvd.nist.gov/vuln/detail/CVE-2026-76835 · CYBERDUDEBIVASH® SENTINEL APEX Evidence Engine v3.0
Provenance and Certification
Report IDCDB-CTI-2026-BC337A76BAC3
Source systemnvd
Source published2026-08-24T18:17:21.570000
Source-record SHA-256bc337a76bac386a55365e98defef38f2f3bd92d7f2c27de3c3591922ba701ad7
Generated UTC2026-08-24T18:59:53.569811Z
Production ModeAI-Native Automated Intelligence — Evidence-Graph Verified
CertificationPublic Intelligence Certification: FLASH_READY (automated evidence-graph certification — see Provenance for the source basis)