CVE-2026-28496 — FOSSBilling Server-Side Template Injection in Twig Rendering

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

1. Identify exposed assets running the affected vendor/product/version combinations (FOSSBilling FOSSBilling).
2. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
3. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-1336

Other CVEs with this weakness →

Public exploits, PoCs and detection templates

Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.

Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 1.91%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

• Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).

Analysis and videos

CVE-2026-28496: FOSSBilling Server-Side Template Injection in Twig Rendering
FOSSBilling versions prior to 0.8.0 contain a Server-Side Template Injection flaw in Twig template rendering, reachable by administrators through email templates, mass mail campaigns, custom payment adapters and the string_render API endpoint. The record states that successful exploitation can lead to information disclosure and remote code execution. Upgrading to 0.8.0 is the stated fix, and no confirmed exploitation in the wild appears in the sources consulted.

Timeline

What happened to this CVE, newest first.

• 2026
• Affected products added · fossbilling/fossbilling
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• SSVC assessment updated
  Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
• Record published
  Oct 13, 2026
• CVSS changed · 9.4
  Oct 13, 2026 · NIST National Vulnerability Database
• Source status changed · → Deferred
  Oct 13, 2026 · NIST National Vulnerability Database
• Record created in this database
  Oct 13, 2026 · NIST National Vulnerability Database
• CVE published
  Jun 23, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

• 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

3 on the record

• www.vulncheck.com/blog/fossbilling-auth-bypass-ssti-rce
  x_refsource_MISC, NIST National Vulnerability Database
• github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-57mv-jm88-66jc
  x_refsource_CONFIRM, NIST National Vulnerability Database
• github.com/FOSSBilling/FOSSBilling/security/advisories/GHSA-78x5-c8gw-8279
  x_refsource_MISC, NIST National Vulnerability Database

Elsewhere on this site

Related CVEs (same products)

• Medium CVE-2026-53648 FOSSBilling: Downloadable product files can be overwritten through filename collisions Jul 6, 2026
• Medium CVE-2026-53647 FOSSBilling vulnerable to unauthenticated API key configuration disclosure via guest Serviceapikey get_info endpoint Jul 6, 2026
• High CVE-2026-53643 FOSSBilling allows low-privileged staff accounts to perform unauthorized actions via admin API endpoints Jul 6, 2026
• Medium CVE-2026-53642 FOSSBilling: Unverified clients can access client-area pages when email confirmation is required Jul 6, 2026
• High CVE-2026-53644 FOSSBilling's missing order-state validation allows clients to read and reset API key secrets for non-active orders Jul 6, 2026
• High CVE-2026-53645 FOSSBilling's missing self-edit prevention in staff permission management allows persistent privilege escalation Jul 6, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

• No fixed version, patch or mitigation documented.
• No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
• No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
• No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-28496 is "FOSSBilling Server-Side Template Injection in Twig Rendering", rated Critical. It affects FOSSBilling (FOSSBilling); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.4 describes technical severity. EPSS 1.91% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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