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01 Record

CVE-2026-40087

LangChain has incomplete f-string validation in prompt templates

MediumPUBLISHEDCNA: GitHub_M
CNA base score5.3 CVSS v3.xCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
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02 Description

LangChain has incomplete f-string validation in prompt templates

03 Exploitation and scoring

Exploitation
Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.
SSVC decision
  • ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
  • AutomatableyesAn attacker can reliably automate reconnaissance through exploitation, so this scales.
  • Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.
CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.
EPSS probability
0.26% probability of exploitation activity in the next 30 days.
EPSS percentile
Equal to or higher than the score of 17.7% of scored records. A rank, not a probability.
NVD base score
5.3 (CVSS v3.x), scored by the NVD independently of the CNA.
NVD CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
NVD analysis status
Analyzed. NVD last modified this record on 2026-10-25.
Red Hat severity
Moderate. Red Hat's rating for its own products, not a CVSS rating.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

04 Metadata

Published
2026-04-09 19:34Z6 MO AGO
Last updated
2026-04-14 14:48Z6 MO AGO
Reserved
2026-04-09
Assigning CNA
GitHub_M
Record state
PUBLISHED
Severity
Medium (CVSS 5.3)
CNA CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weaknesses
  • CWE-1336Improper Neutralization of Special Elements Used in a Template EngineBase
Data version
5.2
Document digest
e36342cbc1646af689113e397a6b217c257019f8603b415ced3c05ec521bc342

05 Affected products

VendorProductVersionsPlatforms
langchain-ailangchain< 0.3.83, >= 1.0.0a1, < 1.2.28—

06 References