# CVE-2026-79771: Nokogiri before 1.19.3 Memory Leak via XSLT Transform

> Attackers can cause denial of service in applications using Nokogiri by triggering a memory leak via null bytes in XSLT transforms.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 25 Aug 2026
- **Updated:** 25 Aug 2026
- **Also known as:** BELL-CVE-2026-79771, DEBIAN-CVE-2026-79771, GHSA-v2fc-qm4h-8hqv, MINI-2mqp-3f9p-m5q4, MINI-2xr9-5pxm-ccjg, MINI-3p7g-7gj8-wgwj, MINI-67vw-x6h4-m935, MINI-7q9p-7569-h9jj, MINI-m8rj-7wf4-hjrv, MINI-mj4g-fpc3-8cjw, MINI-rj4v-cf7j-v2vr, MINI-x27h-cxg7-288p, UBUNTU-CVE-2026-79771

## What is CVE-2026-79771?

CVE-2026-79771 is a medium-severity denial of service vulnerability in sparklemotion nokogiri, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Nokogiri versions before 1.19.3 contain a memory leak in the XSLT Stylesheet transform method when processing Ruby strings containing null bytes. Attackers can exploit this by passing attacker-controlled input with null bytes to transform parameters, causing heap allocations to leak and enabling denial of service against long-running processes.

Weakness: CWE-401 (Missing Release of Memory after Effective Lifetime)

## Which versions are affected by CVE-2026-79771?

2 open source packages ship an affected version, including nokogiri. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `nokogiri` | RubyGems | All versions | 1.19.3 |
| `nokogiri` | RubyGems | All versions | 1.19.3 |

Products: Nokogiri Nokogiri.

## How do I fix CVE-2026-79771?

Upgrade nokogiri to 1.19.3 or later.

## Is CVE-2026-79771 being exploited?

There is no known exploitation of CVE-2026-79771 in the wild and no public exploit code.

## Other vulnerabilities in sparklemotion nokogiri

- [CVE-2026-79770](https://insights.sbomify.com/CVE-2026-79770/): Nokogiri before 1.19.3 ReDoS via CSS selector tokenizer (high 8.7)
- [CVE-2022-23476](https://insights.sbomify.com/CVE-2022-23476/): Unchecked return value from xmlTextReaderExpand in Nokogiri (high 7.5)
- [CVE-2021-41098](https://insights.sbomify.com/CVE-2021-41098/): Improper Restriction of XML External Entity Reference (XXE) in Nokogiri on JRuby (high 7.5)
- [CVE-2012-6685](https://insights.sbomify.com/CVE-2012-6685/): Nokogiri is vulnerable to XML External Entity (XXE) attack (high 7.5)
- [CVE-2026-79772](https://insights.sbomify.com/CVE-2026-79772/): Nokogiri before 1.19.1 Unchecked Return Value canonicalize (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-79771 and fix it if it is affected.

What it is: CVE-2026-79771 is a medium-severity denial of service vulnerability in sparklemotion nokogiri, published on 25 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-79771 in the wild and no public exploit code.

Affected packages and fixed versions:
- nokogiri (RubyGems): affected all versions; fixed in 1.19.3
- nokogiri (RubyGems): affected all versions; fixed in 1.19.3

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-79771/ (Markdown: https://insights.sbomify.com/CVE-2026-79771/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-79771
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-79771
- OSV: https://osv.dev/vulnerability/CVE-2026-79771

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-79771/
Summaries are generated and may contain mistakes; the official description above is the record.