LMFDB: Improper Neutralization of Special Elements Used in a Template Engine
CVE-2026-123198 is a critical-severity improper neutralization of special elements used in a template engine vulnerability in LMFDB, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 01829bd09b692c720aad30c952758a20630573d4 as the first without the flaw, so updating LMFDB to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.84% chance of exploitation within 30 days, higher than 59% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update LMFDB to 01829bd09b692c720aad30c952758a20630573d4 or a later version.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| LMFDB | LMFDB | before 01829bd09b692c720aad30c952758a20630573d4 | 01829bd09b692c720aad30c952758a20630573d4 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (vulncheck.com).
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 9.3 | Critical | CNA (vulncheck.com) |
| CVSS 3.1 | 9.8 | Critical | CNA (vulncheck.com) |
Official description
LMFDB before commit 01829bd contains a server-side template injection vulnerability in the render_knowl function that allows unauthenticated attackers to inject Jinja expressions via request parameters. Attackers can supply crafted query-string values or 'content' data to /knowledge/render/<ID> to reach Python builtins and execute operating system commands as the web application account.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements Used in a Template Engine
The product uses a template engine to insert or process externally-influenced input, but it does not neutralize or incorrectly neutralizes special elements or syntax that can be interpreted as template expressions or other code directives when processed by the engine.
How developers prevent this class of flaw
- Choose a template engine that offers a sandbox or restricted mode, or at least limits the power of any available expressions, function calls, or commands.
- Use the template engine's sandbox or restricted mode, if available.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
Other references
Recent Improper Neutralization of Special Elements Used in a Template Engine vulnerabilities
- 8.8 High severity
- 7.2 High severity
- 8.8 High severity
- 8.8 High severity
- 7.5 High severity
- 8.8 High severity
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