Scriban Affected by Memory Exhaustion (OOM) via Unbounded String Generation (Denial of Service)

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

TemplateContext.LimitToString defaults to 0 (unlimited). While Scriban implements a default LoopLimit of 1000, an attacker can still cause massive memory allocation via exponential string growth. Doubling a string for just 30 iterations generates over 1GB of text, instantly exhausting heap memory and crashing the host process. Because no output size limit is enforced, repeated string concatenation results in exponential memory growth. Proof of Concept (PoC): The following payload executes in under 30 iterations but results in ~1GB string allocation, crashing the process. Impact: An attacker can supply a small template that triggers exponential string growth, forcing the application to allocate excessive memory. This leads to severe memory pressure, garbage collection thrashing, and eventual process termination (DoS). Suggested Fix: Enforce a sensible default limit for string output. Set default LimitToString to 1MB (1,048,576 characters).

Published by the source

19 Mar 2026, 21:31 UTC

Last modified by the source

6 Jul 2026, 13:06 UTC

Source last checked

26 Oct 2026, 17:05 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-5rpf-x9jg-8j5p

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# Patch Next advisory brief: GHSA-5rpf-x9jg-8j5p

Advisory: Scriban Affected by Memory Exhaustion (OOM) via Unbounded String Generation (Denial of Service)
IDs: GHSA-5rpf-x9jg-8j5p
Record: https://patchnext.com/advisories/ghsa-5rpf-x9jg-8j5p (revision 1, source checked 26 Oct 2026, 17:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: scriban.signed 6.6.0; scriban 6.6.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet scriban.signed: affected <= 6.5.8; fixed in 6.6.0
- NuGet scriban: affected <= 6.5.8; fixed in 6.6.0

## Suggested inspection (read-only)
- NuGet scriban.signed: check the installed version with your package manager.
- NuGet scriban: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on scriban.signed, scriban.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-5rpf-x9jg-8j5p (GitHub-reviewed advisory GHSA-5rpf-x9jg-8j5p lists affected ranges: NuGet scriban >=0 =0 <=6.5.8)

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