LangChain is a framework for building agents and LLM-powered applications. Prior to 0.3.84 and 1.2.28, LangChain's f-string prompt-template validation was incomplete in two respects. First, some prompt template classes accepted f-string templates and formatted them without enforcing the same attribute-access validation as PromptTemplate. In particular, DictPromptTemplate and ImagePromptTemplate could accept templates containing attribute access or indexing expressions and subsequently evaluate those expressions during formatting. Second, f-string validation based on parsed top-level field names did not reject nested replacement fields inside format specifiers. In this pattern, the nested replacement field appears in the format specifier rather than in the top-level field name. As a result, earlier validation based on parsed field names did not reject the template even though Python formatting would still attempt to resolve the nested expression at runtime. This vulnerability is fixed in 0.3.84 and 1.2.28.

There are packages installed that are affected by a vulnerability referenced in the following CVE:

  - LangChain is a framework for building agents and LLM-powered applications. Prior to 0.3.84 and 1.2.28,
    LangChain's f-string prompt-template validation was incomplete in two respects. First, some prompt
    template classes accepted f-string templates and formatted them without enforcing the same attribute-
    access validation as PromptTemplate. In particular, DictPromptTemplate and ImagePromptTemplate could
    accept templates containing attribute access or indexing expressions and subsequently evaluate those
    expressions during formatting. Second, f-string validation based on parsed top-level field names did not
    reject nested replacement fields inside format specifiers. In this pattern, the nested replacement field
    appears in the format specifier rather than in the top-level field name. As a result, earlier validation
    based on parsed field names did not reject the template even though Python formatting would still attempt
    to resolve the nested expression at runtime. This vulnerability is fixed in 0.3.84 and 1.2.28.
    (CVE-2026-40087)

ID	Name	Product	Family	Type	Severity
458332	Echo: langchain-core: security update to 1.2.21+echo.2	Tenable Cloud Security	Echo Local Security Checks	Local	medium
458332	Echo: langchain-core: security update to 1.2.21+echo.2	Tenable Self-Hosted Container Security	Echo Local Security Checks	Local	medium
440098	SCA: security update for langchain-core (GHSA-926x-3r5x-gfhw)	Tenable Cloud Security	SCA Checks	Local	medium
440098	SCA: security update for langchain-core (GHSA-926x-3r5x-gfhw)	Tenable Self-Hosted Container Security	SCA Checks	Local	medium

Detections

Analytics

CVE-2026-40087

medium

Tenable Plugins

medium

medium

medium

medium