CVE
fulgur: Unbounded counters() expansion in generated content causes memory/CPU exhaustion (denial of service)
Affects fulgur 0.15.0 up to but not including 0.27.0 when documents use counters() in generated content with many sibling elements. Fixed in 0.27.0.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- Fixed in 0.27.0
- Who is exposed
- Default setups
Do first: Check every install: default setups are affected.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 30/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Default setups
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Fulgur, which converts HTML/CSS to PDF, can be made to exhaust CPU and memory when resolving CSS counters() in generated content, because the expansion is not bounded. An attacker can exploit this remotely and without logging in by submitting a small crafted HTML/CSS payload, which can deny service to the host and other tenants.
Read the original description
fulgur converts untrusted HTML/CSS into PDF, commonly on a server that processes input supplied by many tenants. From version 0.15.0 to before version 0.27.0, resolving the CSS counters(name, sep) function in generated content was bounded neither in the size of a single expansion nor in the aggregate work across an element tree. An attacker able to submit HTML/CSS to a fulgur-based conversion service can trigger CPU and memory exhaustion with a trivially small payload, denying service to the host and any co-tenants. This issue has been patched in version 0.27.0.
Who should check
Teams running fulgur-rs fulgur (Rust crate) between 0.15.0 and 0.27.0, especially services rendering untrusted HTML/CSS to PDF for multiple tenants.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure22/25Default setups, reachable over the network without a login
- Reach?/20Unknown. No tracked technology or package matched
- Severity7.5/10CVSS 7.5
- No patch0/5No signal
What would change the score
- Would score about 70 if added to CISA KEV
- Would score about 65 if CISA's SSVC rates exploitation active
What to do
Check every install: default setups are affected.
Upgrade to a fixed version: 0.27.0.
Workaround: Upgrade to 0.27.0 or later. If upgrading is not immediately possible, validate or constrain untrusted CSS (in particular counter-reset on many sibling elements combined with a long counters() separator) before passing HTML to fulgur.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-68538 (fulgur: Unbounded counters() expansion in generated content 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-2026-68538 (entry last updated 2026-11-11):
Affected:
- fulgur-rs fulgur: from 0.15.0, fixed in 0.27.0
Fixed versions: 0.27.0.
Conditions (all must be true for the bug to be hit):
- Affects fulgur versions from 0.15.0 up to but not including 0.27.0. (source: https://github.com/fulgur-rs/fulgur/security/advisories/GHSA-395p-pj7r-jm42)
- Document uses CSS counter-reset and counters() in generated content (::before/::after) or bookmark-label, with many sibling elements and a long separator. (source: https://github.com/fulgur-rs/fulgur/security/advisories/GHSA-395p-pj7r-jm42)
Setup: the bug is reachable in a default setup; no special feature or setting is needed.
Attacker needs: network access, no login, no user action.
Workaround: Upgrade to 0.27.0 or later. If upgrading is not immediately possible, validate or constrain untrusted CSS (in particular counter-reset on many sibling elements combined with a long counters() separator) before passing HTML to fulgur. (source: https://github.com/fulgur-rs/fulgur/security/advisories/GHSA-395p-pj7r-jm42)
CISA KEV: CVE-2026-68538 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-68538 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-395p-pj7r-jm42
- https://github.com/fulgur-rs/fulgur/commit/ebc75691ad368f1c1a211543313b04da2af466d6
- https://github.com/fulgur-rs/fulgur/releases/tag/v0.27.0
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-2026-68538
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-2026-68538"}.Timeline
- CVE published
- First seen by cve.now
Affected versions
- fulgur-rs fulgur
From 0.15.0 · fixed in 0.27.0
Evidence 4
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
Other links · 2
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-68538
Is CVE-2026-68538 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: cve.now feed data
What does this mean?
Fulgur's handling of CSS counters() in generated content had no limit on how large each expansion could get or how much total work it could do across an element tree. A small crafted HTML/CSS input can therefore use a lot of CPU and memory, which can deny service to the host and any co-tenants.Source: github.com
Which versions are affected by CVE-2026-68538?
fulgur: from 0.15.0 before 0.27.0.Source: cve.now feed data
Am I affected, and how do I check?
Fulgur versions from 0.15.0 up to but not including 0.27.0 are affected. The risky setup is a document that uses counter-reset and counters() in generated content (::before/::after) or bookmark-label, with many sibling elements and a long separator. To check, look at the fulgur version in your dependency manifest or installed package and compare it with 0.27.0.Source: github.com
How do I fix CVE-2026-68538?
Upgrade to fulgur 0.27.0 or later, which caps each counters() expansion. If an upgrade is not immediately possible, validate or constrain untrusted CSS before passing HTML to fulgur, particularly counter-reset on many sibling elements combined with a long counters() separator.Source: github.com