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Response snapshot Oct 27, 2026, 01:44 UTC

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VulnerabilityCVE-2026-73054

SiYuan: A parser differential between the WebSocket keepalive exemption and the session quarantine allows unauthenticated access to the broadcast event stream

Two checks on the same WebSocket request URI parse it differently. The authentication exemption for keepalive sessions matches raw substrings, while the quarantine introduced to contain those sessions reads a parsed query parameter. Because Go's `url.Values.

Published Updated

At a glance

Exploited
Not known
Severity
7.5 High (CVSS 3.1)
Chance of exploitation
0.5% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: github.com/siyuan-note/siyuan/kernel: 0.0.0-20260731131820-67bc300b6ea6. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-c8w8-3pqp-wr83 (opens a new tab)

What happened

### Summary

Two checks on the same WebSocket request URI parse it differently. The authentication exemption for keepalive sessions matches raw substrings, while the quarantine introduced to contain those sessions reads a parsed query parameter. Because Go's `url.Values.Get` returns only the first value for a repeated key, a single URI can satisfy the exemption and still resolve to a non-auth session identity.

The result is that an unauthenticated remote caller connects to the kernel WebSocket with a valid access auth code configured, is placed in the general broadcast pool rather than the quarantined pool, and receives the live event stream.

### Details

Continue reading

**The exemption matches substrings.** `kernel/server/serve.go:1222` on the development branch, `:1074` on master:

```go authOk = strings.Contains(s.Request.RequestURI, "/ws?app=siyuan") && strings.Contains(s.Request.RequestURI, "&id=auth&type=auth") ```

Neither operand is parsed. Any URI containing both literals is exempted, regardless of what the query actually resolves to.

**The quarantine parses.** Commit `1e370e373` added the containment for exempted sessions at `kernel/util/websocket.go:171`:

```go id = session.Request.URL.Query().Get("id") return "auth" == id ```

`url.Values.Get` returns the first value for a repeated key.

**The differential.** For the URI:

``` /ws?app=siyuan&id=main&type=main&id=auth&type=auth ```

- It contains `/ws?app=siyuan` and `&id=auth&type=auth`, so `authOk` is true. No cookie, no JWT and no access auth code are required. - `Query().Get("id")` returns `main`, so `IsAuthSession` is false. `AddPushChan` files the session in `sessions`, the broadcast pool, rather than in `authSessions`. - `Query().Get("type")` returns `main`, so the session matches `BroadcastByType("main", ...)`.

- Without a valid `X-Auth-Token` the publish flag is never set, so `isPublishSession()` does not exclude it either.

Every guard that should have caught the session keys off a different parse than the one that admitted it.

**No origin validation.** `CheckOrigin` does not appear on the `/ws` path, so the cross-origin vector described in the parent advisory also remains available.

**Distinction from the existing broadcast-pool advisory.** GHSA-mw8r-mw84-88v2 concerns the publish port, where an anonymous session is expected to connect and the defect is that broadcast content is not gated for it afterwards. This report concerns the kernel port with an access auth code configured, where the session should never be admitted in the first place.

The leaked data overlaps because both end in the same broadcast pool, but the mechanisms and the affected deployments are different, and gating publish sessions does not close this path.

### Proof of Concept

Kernel port, `--accessAuthCode` set. Three WebSocket connections, none carrying credentials of any kind.

| Socket | Query | Result | |---|---|---| | A, baseline | `?app=siyuan&id=main&type=main` | Rejected, closed 1002, 0 frames | | B, control | `?app=siyuan&id=auth&type=auth` | Connects, 0 frames | | C, attack | `?app=siyuan&id=main&type=main&id=auth&type=auth` | Connects, 19 to 30 frames across two runs |

Socket A establishes that the access auth code is enforced. Socket B establishes that the existing quarantine works exactly as intended, admitting the keepalive session but delivering nothing to it. Socket C differs from B only in the duplicated parameters, and receives the event stream.

Frames observed on socket C included `savedoc` (`"action":"create","data":{"Root":{"ID": ...`), `transactions` (`"action":"updateAttrs"` carrying document titles), `filetreeSortChanged` (the notebook's complete ordered `childIDs`), `create` (a notebook object including its `name`), and `backgroundtask`.

A canary string placed inside a document body did not appear in any frame, on a full-text search of all captured frames.

### Impact

An unauthenticated remote caller obtains the kernel's live event stream on a deployment protected by an access auth code, with no user interaction and no prior knowledge of the instance.

Precisely what is disclosed: document identifiers and titles, notebook identifiers and names, file paths, the complete ordered child structure of notebooks, and the full stream of create, update and delete operations as they occur. Document body content is not present in the observed frames.

That set corresponds to the disclosure claimed by GHSA-xp2m-98x8-rpj6, which means the remediation for that advisory is bypassable rather than incomplete in scope. The absence of origin validation on the endpoint additionally preserves the cross-origin reachability described there.

Confidentiality only. No frames observed permitted writes.

### Suggested fix

Make both checks agree, and stop re-parsing attacker-controlled input after admission.

1. In the exemption, parse the query rather than matching substrings, and require `id` and `type` each to equal `auth` exactly. 2. Reject requests carrying duplicated query keys on this endpoint, so no URI can present two identities. 3. Record the exemption as a flag on the session at connect time, and have `IsAuthSession` read that flag rather than re-parsing the request.

A session admitted under the keepalive exemption is then quarantined by construction, independent of how its URI is read later.

Adding origin validation to `/ws` would additionally close the cross-origin vector.

Affected package ranges reported by GitHub: github.com/siyuan-note/siyuan/kernel: < 0.0.0-20260731131820-67bc300b6ea6

Scores and how they were measured

CVSS base severity

7.5

Version 3.1As of

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.5%

Scored Percentile 45.1%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-c8w8-3pqp-wr83 (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c8w8-3pqp-wr83, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c8w8-3pqp-wr83, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  4. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c8w8-3pqp-wr83, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  5. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c8w8-3pqp-wr83, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  6. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c8w8-3pqp-wr83, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  7. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c8w8-3pqp-wr83, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  8. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c8w8-3pqp-wr83, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  9. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c8w8-3pqp-wr83, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  10. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-c8w8-3pqp-wr83, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  11. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-73054, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 23). SiYuan: A parser differential between the WebSocket keepalive exemption and the session quarantine allows unauthenticated access to the broadcast event stream (CVE-2026-73054). https://kevwire.com/record/CVE-2026-73054

MLA

"SiYuan: A parser differential between the WebSocket keepalive exemption and the session quarantine allows unauthenticated access to the broadcast event stream (CVE-2026-73054)." KEVWire, 23 Oct. 2026, kevwire.com/record/CVE-2026-73054.

Chicago

KEVWire. "SiYuan: A parser differential between the WebSocket keepalive exemption and the session quarantine allows unauthenticated access to the broadcast event stream (CVE-2026-73054)." Last modified October 23, 2026. https://kevwire.com/record/CVE-2026-73054.

Evidence summary (plain text)

SiYuan: A parser differential between the WebSocket keepalive exemption and the session quarantine allows unauthenticated access to the broadcast event stream (Oct 23, 2026).
Two checks on the same WebSocket request URI parse it differently. The authentication exemption for keepalive sessions matches raw substrings, while the quarantine introduced to contain those sessions reads a parsed query parameter. Because Go's `url.Values.Get` returns only the first value for a repeated key, a single URI can satisfy the exemption and still resolve to a non-auth session identity.

The result is that an unauthenticated remote caller connects to the kernel WebSocket with a valid access auth code configured, is placed in the general broadcast pool rather than the quarantined pool, and receives the live event stream.
CVSS 7.5 (version 3.1; evidence as of Oct 23, 2026; https://github.com/advisories/GHSA-c8w8-3pqp-wr83).
EPSS 0.5% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-73054&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-c8w8-3pqp-wr83: https://github.com/advisories/GHSA-c8w8-3pqp-wr83
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo1MTozMFrOAAf0Mg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0OToxMlrOAAf0LQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NzoxN1rOAAf0Kg%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTozNlrOAAf0Jw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0NTowNVrOAAf0JQ%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0Mzo0NVrOAAf0Iw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QyMDo0MzozMVrOAAf0Ig%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc&after=Y3Vyc29yOnYyOpK0MjAyNi0xMC0yM1QxODozNTowMVrOAAZRcw%3D%3D
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-73054&date=2026-10-26
Record ID: CVE-2026-73054.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 27, 2026, 01:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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