CVE-2026-85734: lightrag-hku: No Rate Limiting on /login Endpoint Allows Brute-Force Attacks

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.4%, percentile 28: FIRST’s model estimates a 0.4% chance of exploitation activity in the next 30 days, higher than 28% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes lightrag-hku (PyPI) < 1.5.5, fixed in 1.5.5. Check your lockfile, including transitive dependencies.

What it is

LightRAG provides simple and fast retrieval-augmented generation. Prior to 1.5.5, the POST /login endpoint in lightrag/api/lightragserver.py does not impose a rate limit, account lockout, delay, or counter for failed authentication attempts. A network attacker can submit password guesses at full request speed until a valid account password is found. Successful credential recovery grants authenticated access to documents, the knowledge graph, and administrative operations. This issue is fixed in version 1.5.5.

From the GitHub advisory

Summary The POST /login endpoint has no rate limiting, account lockout, or delay on failed attempts. An attacker can submit unlimited password guesses at full network speed.

Details

A search for slowapi, ratelimit, lockout, or throttle in lightrag/api/ returns zero results.

PoC

Impact Improper restriction of authentication attempts. Any network-reachable attacker can brute-force user passwords without restriction. Once credentials are recovered, the attacker gains full authenticated access to all documents, knowledge graph, and administrative operations.

Weakness type: CWE-307.

Product: lightrag-hku (PyPI) · Assigned by: GitHub_M · Published: 2026-09-22

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.36% probability of exploitation activity in the next 30 days; percentile 28.

Timeline

• 2026-09-22 — CVE record last updated
• 2026-09-22 — CVE record published by GitHub_M
• 2026-09-22 — GitHub-reviewed advisory GHSA-frch-4w6v-q5xx published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-frch-4w6v-q5xx github.com
2. CVE.org record CVE-2026-85734 cve.org
3. NVD entry CVE-2026-85734 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com

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