AhsayCBS system password-check bypass

AhsayCBS system password-check bypass (CVE-2026-105133)

Source and API bundle

cve.now entry.

Eden terminates the HTTP connection to the affected product, evaluates a declarative policy and — in tier 2 — a separately compiled native Rust module under signed module authority, before any byte reaches the application. It does not patch the affected component; the vendor's fixed release remains the durable repair.

Status: live two-tier remediation recorded 2026-11-11 on the installed eden-product-release:1.103.0-single lab container (image sha256:809293e1f0b525ac04698d1fa8d7ffdc66cbee1ff690b082ba26b4d050f08416). Both bypass branches of the fixture's login check are refused (the bypass parameter and the missing-password form); ordinary credential checks pass.

The vulnerability

Improper authentication in the AhsayCBS system password check lets a remote attacker bypass login protections (v7-v10; earlier hotfixes incomplete). KEV-listed.

The Eden patch

Tier 1 — declarative policy (blunt, fail-closed): deny on the affected route family — takes the whole surface offline, legitimate calls included.

Tier 2 — native module: gabriel_ahsayauth_v1, binary SHA-256 53cda7c4ed3e240a17da33acffb9a398242da24e8395ebaa7dff475062e52cb4 (source 0af7371242ff2ffda9edd57c4ba4559a29d07023fd5c2e4232bd52e38d0663c7). See the comparison table for what it keys, and the honest scope for what it cannot.

Measured comparison (live, 2026-11-11)

Performance trace (Eden telemetry, live 2026-11-11)

Measured with Eden's built-in request telemetry (gateway.request.baseline spans, read back through /api/v1/analytics/telemetry?signal=traces), not client wall-clock. Latency Eden introduces per remediation arm for this case:

Eden-added latency for the tier-2 remediation: benign requests complete in 447 µs mean (p50 426 µs, p95 591 µs) in-product, module evaluation included. Honest scope: lab fixtures on one host, fresh connection per measured request, warm requests only; module reactivated shards 2/2 with a fresh signed statement per measurement; spans carry the full authority lineage (module SHA-256, operation, publication). Not the EDEN-3640 performance qualification contract.

Tested against: eden-product-release:1.103.0-single (image sha256:809293e1f0b525ac…, build target eden_service_single, tooling revision 81a0724a…). Raw data: module2/telemetry-ab/ahsayauth-telemetry.json and module2/tier1-ab/ahsayauth-tier1.json.

Authority lifecycle and negatives

Driven through the full signed lifecycle (module2/evidence/ahsayauth-module.json): enroll_key (Ed25519 public key), independent-host inventory, inspect (bindings derived without mapping code), host approve, signed admit (prepared, serving_now: false), activate — receipt serving_now: true, applied_shards == expected_shards (2/2). Negatives held: read-only inspect -> 403, tampered statement binding -> 400, flipped signature bit -> 403. revoke failed the interlay closed (503, nothing forwarded, zero backend effects) and a fresh host approval plus a newly signed activation restored the module's behavior.

Honest scope

The fixture replicates the delivery shape and exploit prerequisite with a harmless marker effect; no real vendor component runs here. The module keys only the primitive listed above — bypass variants (encodings, alternate routes, crafted members other than the one keyed) are not bypass-tested and are out of scope; the rule is a lab-grade partial by construction. The vendor's fixed release remains the durable repair. Perf: request-path A/B not re-run for this batch (see README); activation telemetry measured ~0.14 s one-time load.

Cost record (per-CVE ledger)

$0.0789 USD (marginal session growth: 1,128,044 in + 46 out tokens, 3 turns; shared debug windows overlap).

Evidence appendix

• cve.now entry
• Raw evidence: gabriel-2026-11-11/module2/evidence/ahsayauth-module.json
• Deployment: installed eden-product-release:1.103.0-single lab container (image sha256:809293e1f0b525ac04698d1fa8d7ffdc66cbee1ff690b082ba26b4d050f08416)
• Skill: eden-vulnerability-remediation

Decision flow

This is the available form-byte predicate. It neither verifies a password nor establishes coverage of every Ahsay login path.

Complete native module source

The complete available source for gabriel_ahsayauth_v1 is reproduced below from the reviewed repository snapshot. The source SHA-256 is 0af7371242ff2ffda9edd57c4ba4559a29d07023fd5c2e4232bd52e38d0663c7. This identifies the source bytes, rather than independently proving the binary build or the recorded test results. The case’s experiment status and limitations still apply, including any failed import, partial coverage, or withdrawn claim. Original source comments are preserved verbatim.

//! Gabriel module: refuse the system-password-check bypass parameter (CVE-2026-105133 shape)
//!
//! CVE-2026-105133: improper authentication in the AhsayCBS system
//! password check lets a remote attacker bypass login protections.
//! This module refuses login bodies carrying the bypass primitive;
//! ordinary credential checks pass unchanged. no_std; no allocator, storage, background work or state.

#![no_std]

use core::mem::size_of;
use core::panic::PanicInfo;
use eden_gateway_remediation::message::{Availability, MessageInput};
use eden_gateway_remediation::module::{
    ApiHeader, CONTINUE, Decision, EDIT, EditSink, Edits, Failure, ModuleOutput, NEED_MORE, REFUSE, RemediationModule,
};
use eden_gateway_remediation::native_http_v3::{self as http, Api, Input, Request};

/// Route prefix in scope.
const ROUTE: &[u8] = b"/cb5/loginModule";

/// The byte primitives this module refuses on that route.
static NEEDLES: [&[u8]; 1] = [b"sys_pwd_bypass"];

fn find(haystack: &[u8], needle: &[u8]) -> Option<usize> {
    if haystack.len() < needle.len() || needle.is_empty() {
        return None;
    }
    let mut i = 0usize;
    while i + needle.len() <= haystack.len() {
        let mut j = 0usize;
        let mut same = true;
        while j < needle.len() {
            if haystack[i + j] != needle[j] {
                same = false;
                break;
            }
            j += 1;
        }
        if same {
            return Some(i);
        }
        i += 1;
    }
    None
}

struct gabriel_ahsayauth_v1;

impl RemediationModule<Request<'_>> for gabriel_ahsayauth_v1 {
    fn evaluate(&self, request: &Request<'_>, edits: &mut Edits<'_>) -> Result<Decision, Failure> {
        let _ = edits;
        let _ = match request.header_count() {
            Availability::Ready(count) => count,
            Availability::NeedMore => return Ok(Decision::NeedMore),
            Availability::Unavailable => return Err(Failure),
        };
        let message = request.message();
        let head = message.prefix();
        let line_end = head.iter().position(|&b| b == b'\r').unwrap_or(head.len());
        let request_line = &head[..line_end];
        let path_at = request_line.iter().position(|&b| b == b' ').unwrap_or(request_line.len());
        let target = &request_line[path_at + 1..];
        if !target.starts_with(ROUTE) {
            return Ok(Decision::Continue);
        }
        if !message.is_complete() {
            return Ok(Decision::NeedMore);
        }
        let body_range = match request.body_range() {
            Availability::Ready(range) => range,
            Availability::NeedMore => return Ok(Decision::NeedMore),
            Availability::Unavailable => return Err(Failure),
        };
        let body = match message.bytes(body_range)? {
            Availability::Ready(bytes) => bytes,
            Availability::NeedMore => return Ok(Decision::NeedMore),
            Availability::Unavailable => return Err(Failure),
        };
        if NEEDLES.iter().any(|n| find(body, n).is_some()) {
            return Ok(Decision::Refuse);
        }
        // The lab fixture models a second bypass branch: a system-user login
        // form that omits the password field entirely. Presence of `sys_user=`
        // without `sys_password=` is refused for the same reason as the
        // marker form: the vulnerable check must not decide on markers.
        if find(body, b"sys_user=").is_some() && find(body, b"sys_password=").is_none() {
            return Ok(Decision::Refuse);
        }
        Ok(Decision::Continue)
    }
}

static API: Api = Api {
    header: ApiHeader { version: http::VERSION, table_size: size_of::<Api>() as u32 },
    input_size: size_of::<Input>() as u32,
    output_size: size_of::<ModuleOutput>() as u32,
    sink_size: size_of::<EditSink>() as u32,
    message_size: size_of::<MessageInput>() as u32,
    state_bytes: 0,
    capabilities: CONTINUE | REFUSE | NEED_MORE | EDIT,
    required_inputs: 0,
    evaluate: Some(evaluate),
};

unsafe extern "C" fn evaluate(input: *const Input, sink: *const EditSink, output: *mut ModuleOutput) -> i32 {
    unsafe { http::invoke(&gabriel_ahsayauth_v1, input, sink, output) }
}

#[unsafe(no_mangle)]
pub extern "C" fn eden_http_remediation_v3() -> *const Api {
    &API
}

#[panic_handler]
fn panic(_information: &PanicInfo<'_>) -> ! {
    loop {
        core::hint::spin_loop();
    }
}