CVE-2025-59340: jinjava has Sandbox Bypass via JavaType-Based Deserialization

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 2.1%, percentile 82: FIRST’s model estimates a 2.1% chance of exploitation activity in the next 30 days, higher than 82% of all scored CVEs (elevated). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes com.hubspot.jinjava:jinjava (Maven) = 2.8.0, fixed in 2.8.1; com.hubspot.jinjava:jinjava (Maven) >= 2.7.0, < 2.7.5, fixed in 2.7.5. Check your lockfile, including transitive dependencies.

What it is

jinjava is a Java-based template engine based on django template syntax, adapted to render jinja templates. Priori to 2.8.1, by using mapper.getTypeFactory().constructFromCanonical(), it is possible to instruct the underlying ObjectMapper to deserialize attacker-controlled input into arbitrary classes. This enables the creation of semi-arbitrary class instances without directly invoking restricted methods or class literals. As a result, an attacker can escape the sandbox and instantiate classes such as java.net.URL, opening up the ability to access local files and URLs(e.g., file:///etc/passwd). With further chaining, this primitive can potentially lead to remote code execution (RCE). This vulnerability is fixed in 2.8.1.

From the GitHub advisory

Summary

jinjava’s current sandbox restrictions prevent direct access to dangerous methods such as getClass(), and block instantiation of Class objects. However, these protections can be bypassed.

By using mapper.getTypeFactory().constructFromCanonical(), it is possible to instruct the underlying ObjectMapper to deserialize attacker-controlled input into arbitrary classes. This enables the creation of semi-arbitrary class instances without directly invoking restricted methods or class literals.

As a result, an attacker can escape the sandbox and instantiate classes such as java.net.URL, opening up the ability to access local files and URLs(e.g., file:///etc/passwd). With further chaining, this primitive can potentially lead to remote code execution (RCE).

Details

Weakness type: CWE-1336.

Product: com.hubspot.jinjava:jinjava (Maven) · Assigned by: GitHub_M · Published: 2025-09-17

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: none
• Scope: unchanged

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact total.
• FIRST EPSS (model of 2026-10-21): 2.11% probability of exploitation activity in the next 30 days; percentile 82.

Timeline

• 2025-09-17 — CVE record published by GitHub_M
• 2025-09-17 — GitHub-reviewed advisory GHSA-m49c-g9wr-hv6v published (critical)
• 2025-09-18 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-m49c-g9wr-hv6v github.com
2. CVE.org record CVE-2025-59340 cve.org
3. NVD entry CVE-2025-59340 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com
5. github.com github.com

Critical Maven advisories · Today’s Security Digest