CVE-2026-73056Disclosure

LOWCVSS 9.3 · CRITICAL

Exploit discussion active in current signal (1 latest mentions)

Immediate actions

Patch affected systems immediately
Hunt for exploitation attempts and persistence artifacts
Increase monitoring for publicly documented tradecraft

Recommended action window: High priority (within 72h)

NVD description

SiYuan kernel versions before 3.7.4 contain an improper restriction of excessive authentication attempts vulnerability in the CheckAuth() middleware. The middleware accepts the API token (Conf.Api.Token) via an Authorization header (Token/Bearer) or a ?token= query parameter, and neither path is protected by the application's CAPTCHA/lockout mechanism (NeedCaptcha/WrongAuthCount). As a result, an unauthenticated remote attacker can perform unlimited automated guesses of the API token, particularly when a short or weak custom token has been configured, and upon success gains full RoleAdministrator access enabling arbitrary file operations and SQL queries.

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2.0/ 10 priority

Sources & remediation

Other references

Weakness type (CWE)

CWE-307

Priority

LOW

Exploitation

NONE

PoC

YES

Patch

AVAILABLE

Momentum

NONE

Threat summary

Public PoC is present in monitored signal
Patch or workaround signal is available
1 mentions across 1 observed day

What's happening

PoC mentioned or linked in 1 signal
Patch or workaround mentioned in 1 signal
Technical details provided in 1 signal
Disclosure: 1 classified signal
1 total mentions across 1 day

Deep dive

Activity timeline1 mentions / 1d

Signal classification1 categories

Disclosure

1100.0%

Referenced assets1 URL

By indicator

https://www.valtersit.com/cve/CVE-2026-73056/

Full discourse1 post

Hugo | DevOps | Cybersecurity 🇱🇻@HugoValters46d
Disclosure
CVE-2026-73056 - Critical auth bypass in SiYuan kernel <3.7.4. Unauthenticated attackers can brute-force API tokens via CheckAuth() middleware, no lockout. CVSS 9.8. Update immediately. #CVE #SiYuan #infosec https://www.valtersit.com/cve/CVE-2026-73056/ #CVE #infosec #SysAdmin #cybersecurity #Linux #devsecops #devops #developer #sysadmin #100daysofcode #git #github #gitlab #redteam #blueteam #ethicalhacker #ethicalhacking #cybersecurityawareness #cybersecurity #cybersecuritynews #cybersecuritytips #python #hacker #linux #kali #ubuntu #debian #ukraine #spain #ireland #unitedkingdom #canada #finland #estonia #lithuania #ireland #hungary #denmark #norway #malta #mexico
Post summary
CVE‑2026‑73056 is a critical authentication bypass in SiYuan kernel <3.7.4, allowing unauthenticated brute‑force of API tokens. Users are urged to apply the immediate update to mitigate the high‑severity risk.
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