CVE-2026-75513: Marten's LINQ provider has SQL injection via unescaped string literals

Should you act?

Critical, preconditions apply

Severe if exploited, but exploitation needs conditions that may not apply to you. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
• EPSS 0.5%, percentile 39: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 39% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Needs an account (low (any account)). Exposure depends on who can log in.
• Only applies if your dependency tree includes Marten (NuGet) >= 7.0.0, <= 9.12.0, fixed in 9.13.0. Check your lockfile, including transitive dependencies.

What it is

Marten is a .NET Transactional Document DB and Event Store on PostgreSQL. From version 7.0.0 until 9.13.0, several Marten LINQ and tenant-management paths interpolate runtime, potentially attacker-controlled strings into single-quoted SQL literals without escaping or parameterization. The primary confirmed vector is a dictionary indexer key used by Where filters in src/Marten/Linq/Members/Dictionaries/DictionaryItemMember.cs. Additional affected sinks include SelectParser.cs, DatabaseScopedTenantPartitions.cs, and DeleteAllForTenant.cs reached through IEventStore.DeleteProjectionProgressAsync, while DictionaryContainsKeyFilter.cs (Newtonsoft serializer only; System.Text.Json is not affected) handles ContainsKey calls. Events/Daemon/Internals/EventLoader.cs contains a related per-tenant partition-pruning literal that the advisory identifies as a defense-in-depth sink. A crafted single quote can escape the generated literal, enabling filter or multi-tenant authorization bypass and blind data exfiltration, and deployments that permit semicolon-batched Npgsql statements may also allow data modification. This issue is fixed in version 9.13.0.

From the GitHub advisory

Several code paths in Marten's LINQ provider and tenant-management internals interpolated a runtime, potentially attacker-influenced value into generated SQL as a single-quoted string literal without escaping or parameterization. A value containing a single quote (') could break out of the literal and inject arbitrary SQL.

The primary vector is a Dictionary indexer key used in a Where filter — Where(x => x.Attributes[key] == v) — a common "filter by attribute name" / EAV pattern. It is confirmed with an executed proof-of-concept and yields filter / multi-tenant authorization bypass (returning other tenants' rows) and blind data exfiltration. Where the application permits ;-batched statements (Npgsql default), data modification is also possible.

Affected sinks

- Linq/Members/Dictionaries/DictionaryItemMember.cs — dictionary indexer key (primary, confirmed PoC) - Linq/Members/Dictionaries/DictionaryContainsKeyFilter.cs — Dictionary.ContainsKey(key) (Newtonsoft serializer only; System.Text.Json escapes the quote) - Linq/Parsing/SelectParser.cs — a constant string projected through Select(x => new { L = runtimeString }) - Internal/Operations/DeleteAllForTenant.cs — tenant id reaching per-tenant projection teardown via IEventStore.DeleteProjectionProgressAsync (an in-code comment wrongly claimed the value was validated) - Schema/DatabaseScopedTenantPartitions.cs — tenant id inlined into FOR VALUES IN ('...') partition DDL - Events/Daemon/Internals/EventLoader.cs (defense-in-depth) — per-tenant partition-pruning literal

Proof of concept (primary vector)

Weakness type: CWE-89.

Product: Marten (NuGet) · Assigned by: GitHub_M · Published: 2026-09-16

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: low (any account)
• User interaction: none
• Scope: changed (can affect other components)

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 poc, automatable no, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 0.47% probability of exploitation activity in the next 30 days; percentile 39.

Timeline

• 2026-09-16 — CVE record published by GitHub_M
• 2026-09-17 — GitHub-reviewed advisory GHSA-rfx3-98h7-v3xp published (critical)
• 2026-09-19 — 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-rfx3-98h7-v3xp github.com
2. CVE.org record CVE-2026-75513 cve.org
3. NVD entry CVE-2026-75513 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

Critical NuGet advisories · Today’s Security Digest