Vulnerability in nokogiri (CVE-2026-79770)
Summary
Vulnerability in nokogiri (CVE-2026-79770). Risk of unauthorized operations or information disclosure. Exploitable via Regexp.timeout. Mitigation: upgrade to 1.19.3 or later.
Original description
The description as published by the source.
Summary
Nokogiri's CSS selector tokenizer contains regular expressions whose construction may result in exponential regex backtracking on adversarial selectors. Three ReDoS vectors are addressed in this release:
- String-literal tokenization on certain unterminated quoted-string input.
- String-literal tokenization on a separate class of hex-escape-rich input.
- Identifier tokenization on hex-escape-rich input.
The public CSS selector methods that funnel through the affected tokenizer are Nokogiri::CSS.xpath_for, Node#css, Node#at_css, Searchable#search, and CSS::Parser#parse.
Mitigation
Upgrade to Nokogiri >= 1.19.3.
If users are unable to upgrade, two options are available:
- Avoid the use of attacker-controlled text in CSS selectors. Applications that only pass developer-authored selectors to Nokogiri are not directly exposed.
- Set global
Regexp.timeout(Ruby 3.2+, JRuby 9.4+) to bound parse time.
Severity
The Nokogiri maintainers have evaluated this as High Severity (CVSS 7.5, AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
An attacker able to inject user-supplied text into a CSS selector parse method can cause exponential backtracking, resulting in a potential denial of service.
Resources
Credit
Vector 1 was responsibly reported by @colby-swandale. Vectors 2 and 3 were discovered by @flavorjones during the response to the or…
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-79770 has been found in nokogiri.
Attackers can target a specific entry point like Regexp.timeout over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade nokogiri to 1.19.3 or later.
If unsure, ask your IT team or search "nokogiri CVE-2026-79770" on the vendor's site.
CVE-2026-79770 (nokogiri) — CWE-1333 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: Regexp.timeout
Patched: 1.19.3 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-1333) exists in nokogiri. Attackers reach the vulnerable code path via Regexp.timeout without authentication.
Check the vendor advisory for the affected versions of nokogiri. Attack surface: Regexp.timeout.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 1.19.3.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'nokogiri' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
grep -r 'nokogiri' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
nokogiriを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade nokogiri to 1.19.3ステージング環境で 1.19.3 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- web github.com
- web nvd.nist.gov
- web vulncheck.com
- web github.com
- web github.com