CVE-2026-55255
CVE-2026-55255 is a security flaw in Langflow, a tool for building AI apps. Attackers can reach parts of Langflow that should be locked to them. The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 7 Jul 2026.[1]
Langflow is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Langflow has published a fix or advice.
Description
CISA calls it an authorization bypass through user-controlled key in Langflow Langflow. In its words: “Langflow contains an authorization bypass through user-controlled key vulnerability which allows an authenticated attacker to execute any flow belonging to another user by specifying the victim's flow ID in the request.”[1]
The CVE record adds: “Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.1, an Insecure Direct Object Reference (IDOR) vulnerability in /api/v1/responses endpoint allows an authenticated attacker to execute any flow belonging to another user by specifying the victim's flow ID in the request. This vulnerability is fixed in 1.9.1.”[2]
The underlying weakness is authorization bypass (CWE-639), in MITRE’s list of common software weaknesses.
It scores 8.4 out of 10 on the Common Vulnerability Scoring System, which rates it high, scored by the organisation that published the CVE using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Langflow’s advisory has them[3]. CISA names the product as Langflow Langflow.
Most families won’t have Langflow; it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 7 Jul 2026, 14 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 10 Jul 2026 to fix it.[1]
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at under 1%. That’s in the top 41% of the flaws it scores.[4]
CISA assesses it as not automatable: each attack takes some work.
CISA doesn’t say who was attacked, or how.
Fix
Langflow has published a fix or advice.[3] CISA’s required action: “Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes).”[1]
- Check whether you use it.Langflow is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 10 Jul 2026 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 8.4.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at under 1%.[4] |
See also
Other Langflow flaws
- CVE-2026-0770: inclusion of functionality from untrusted control sphere ·
- CVE-2025-34291: origin validation error ·
- CVE-2026-33017: code injection ·
- CVE-2025-3248: missing authentication ·
Added the same day
- CVE-2026-56290, Joomlack Page Builder: improper access control ·
- CVE-2026-48908, JoomShaper SP Page Builder: unrestricted upload of file with dangerous type ·
- CVE-2026-48282, Adobe ColdFusion: path traversal ·
Every Langflow flaw on CISA’s list · Everything added in July 2026
References
- ^ Cybersecurity and Infrastructure Security Agency. “Langflow Authorization Bypass Through User-Controlled Key Vulnerability”. Known Exploited Vulnerabilities Catalog, added 7 Jul 2026.
- ^ National Institute of Standards and Technology. “CVE-2026-55255 Detail”. National Vulnerability Database, published 23 Jun 2026.
- ^ Langflow. Advisories and fixes: github.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.009, percentile 59.3, 31 Oct 2026.
- CVE Program. “CVE-2026-55255”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.