Jiffy Intel — Threat intelligence for AI artifacts

Summary

Multiple community MCP servers pin an lxml version with CVE-2025-37890 (XML External Entity attack). Exploit requires the MCP to parse untrusted XML. Patch available upstream but not propagated to the MCP registry.

Severity & confidence

Severity

High

Credible abuse path with meaningful impact on confidentiality, integrity, or availability. Remediate on a short timeline; do not wait for the next sprint cycle.

Confidence

Confirmed

Observed directly by Jiffy scanners or validated by multiple independent sources. Indicators are reliable enough to drive automated action.

Indicators

Observed patterns and artifacts associated with this entry. Each indicator can be copied into your detection stack or SIEM.

```
lxml\s*==\s*[45]\.\d
```
```
lxml<4\.9\.4
```

Detection rule

A YARA-style pseudo-rule auto-generated from the indicators above. Useful as a starting point — adapt the syntax for your target detection platform.

YARA-style pseudo-rule

rule jiffy_ti_2026_000009
{
    meta:
        source = "jiffy-intel"
        severity = "high"
        description = "Auto-generated from Jiffy Intel indicators"
    strings:
    $content_pattern_0 = "lxml\\s*==\\s*[45]\\.\\d"
    $content_pattern_1 = "lxml<4\\.9\\.4"
    condition:
        $content_pattern_0 or $content_pattern_1
}

Auto-generated from the indicators above. Adapt syntax for your detection stack before deploying.

Affected tools

Tool	Versions	Status
MCP servers (any)	`lxml<5.3.0`	vulnerable

Example artifacts

Sanitized examples of artifacts Jiffy has observed exhibiting this pattern. Publisher handles are redacted; version ranges and status reflect the most recent scan.

python-docs-mcpMCP server
Still live
Source
MCP Registry
Versions
0.5.0 – 0.5.4
First observed
Mar 11, 2026
Last observed
Apr 8, 2026
Bundled lxml 4.6.3 — CVE-2021-43818 XXE. Unpatched at last check.
xml-parser-mcpMCP server
Under review
Source
Community registry
Versions
1.2.x
First observed
Mar 18, 2026
confluence-reader-mcpMCP server
Still live
Source
MCP Registry
Versions
1.0.0
First observed
Mar 25, 2026
Vulnerable bundle; maintainer notified.

How to remediate

01Pin lxml >= 5.3.0 in MCP servers that parse XML.
02Jiffy scanner flags pinned-vulnerable dependencies in the vuln overlay (PRD 8).

Timeline & sources

Timeline

First observedApr 12, 20265 days ago
Last updatedApr 12, 20265 days ago
PublishedApr 11, 20266 days ago

Sources

curatedexternal_partner

References

nvd.nist.govNVD

CVE-2025-37890

https://nvd.nist.gov/vuln/detail/CVE-2025-37890

github.comGitHub

lxml security advisory

https://github.com/lxml/lxml/security/advisories

Related intel

Other entries of type Vuln Dependency, or the most recent published entries if no same-type matches exist.

OtherLow

.cursorrules contains large wall-of-text that pushes user intent out of context

.cursorrules whose rule body exceeds 20 000 characters of filler content. Each agent invocation consumes the rule, leaving limited context for the user prompt. Not a direct exfiltration primitive — a budget-starvation attack.

Jiffy IntelApr 28

BackdoorHigh

Skill writes config that hooks into Claude Desktop stdio MCP bridge

Skill modifies the user's Claude Desktop config to register an MCP server pointing at localhost. The server is supplied by the same skill and serves as a persistent interposer between the agent and tool calls, logging all tool arguments.

Jiffy IntelApr 28

Malicious SkillHigh

MCP server's install script drops a skill into ~/.claude/skills/

MCP server whose install path (`pip install`, `npm i`) includes a side-effect that writes a skill file under the user's Claude skills directory. Installing the MCP silently installs a skill the user never consented to.

Jiffy IntelApr 28

MCP server bundles outdated lxml with known XXE CVE

Summary

Severity & confidence

High

Confirmed

Indicators

Detection rule

Affected tools

Example artifacts

How to remediate

Timeline & sources

Timeline

Sources

References

CVE-2025-37890

lxml security advisory

Scan for patterns like this