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NVD / CVE Program· CNA GitHub_M

CVE-2026-40478: Improper neutralization of specific syntax patterns for unauthorized expressions in Thymeleaf

Noroxi assessment

Priority: Monitor (action score 36/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 1.1% (FIRST EPSS); higher than 65.6% of all records.
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: thymeleaf thymeleaf 3.1.4.RELEASE.

Low priority for now. Upgrade to thymeleaf thymeleaf 3.1.4.RELEASE or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Thymeleaf is a server-side Java template engine for web and standalone environments. Versions 3.1.3.RELEASE and prior contain a security bypass vulnerability in the the expression execution mechanisms. Although the library provides mechanisms to prevent expression injection, it fails to properly neutralize specific syntax patterns that allow for the execution of unauthorized expressions. If an application developer passes unvalidated user input directly to the template engine, an unauthenticated remote attacker can bypass the library's protections to achieve Server-Side Template Injection (SSTI). This issue has ben fixed in version 3.1.4.RELEASE.

CriticalCVSS 9.0 · v3.1—No exploit Fix available
Published
Apr 17, 2026
Updated
Oct 26, 2026
EPSS
1.1% · 65th percentile

Report tools

JSON

Action score

36

Monitor

Low priority for now.

CVSS
36 / 40 · 9.0 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
total

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · GitHub_M
9.1
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-40478

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
thymeleafthymeleaf

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • thymeleaf thymeleafbefore 3.1.4

Versions reported by the vendor

Affected version ranges reported by the assigning authority (GitHub_M). Independent of NVD's CPE analysis and usually ahead of it.

  • thymeleaf org.thymeleaf:thymeleaf-spring5

    • < 3.1.4.RELEASEaffected

  • thymeleaf org.thymeleaf:thymeleaf-spring6

    • < 3.1.4.RELEASEaffected

  • thymeleaf thymeleaf

    • < 3.1.4.RELEASEaffected

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Mavenorg.thymeleaf:thymeleafbefore 3.1.4.RELEASE3.1.4.RELEASE
Mavenorg.thymeleaf:thymeleaf-spring5before 3.1.4.RELEASE3.1.4.RELEASE
Mavenorg.thymeleaf:thymeleaf-spring6before 3.1.4.RELEASE3.1.4.RELEASE

Same product

thymeleaf: all records

Other highest-scoring records for the same primary product.

  • CVE-2021-43466In the thymeleaf-spring5:3.0.12 component, thymeleaf combined with specific scenarios in template injection may lead to remote code executio
    40Plan
  • CVE-2026-41901Thymeleaf: Improper recognition of unauthorized syntax patterns in sandboxed Thymeleaf expressions
    36Monitor
  • CVE-2026-40477Improper restriction of the scope of accessible objects in Thymeleaf expressions
    36Monitor

Published before and after this one in the same product

  • ← EarlierCVE-2023-38286Jul 14, 2023 · Thymeleaf through 3.1.1.RELEASE, as used in spring-boot-admin (aka Spring Boot Admin) through 3.1.1 and other products, allows sandbox bypas
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
thymeleaf thymeleaf3.1.4.RELEASE · descriptionVendor (CNA)
Maven:org.thymeleaf:thymeleaf3.1.4.RELEASEPackage registry (OSV)
Maven:org.thymeleaf:thymeleaf-spring53.1.4.RELEASEPackage registry (OSV)
Maven:org.thymeleaf:thymeleaf-spring63.1.4.RELEASEPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-404770 days apartImproper restriction of the scope of accessible objects in Thymeleaf expressions
    36Monitor
  • CVE-2026-4190125 days apartThymeleaf: Improper recognition of unauthorized syntax patterns in sandboxed Thymeleaf expressions
    36Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
high · data or configuration can be modified
Availability
high · the service can be disrupted

Impact can extend beyond the vulnerable component (scope changes).

Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-917 · Improper Neutralization of Special Elements used in an Expression Language Statement ('Expression Language Injection')

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Show all references (4 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records