Vulnerability in concurrent-ruby (CVE-2026-54904)
Summary
Vulnerability in concurrent-ruby (CVE-2026-54904). Risk of unauthorized operations or information disclosure. Exploitable via compare_and_set. Mitigation: upgrade to 1.3.7 or later.
Original description
The description as published by the source.
concurrent-ruby is a modern concurrency tools for Ruby. Prior to 1.3.7, Concurrent::AtomicReference#update can enter a permanent busy retry loop when the current value is Float::NAN. The issue is caused by the interaction between AtomicReference#update, which retries until compare_and_set(old_value, new_value) succeeds; Numeric compare_and_set, which checks old == old_value before attempting the underlying atomic swap.; and Ruby NaN semantics, where Float::NAN == Float::NAN is always false. As a result, once an AtomicReference contains Float::NAN, calling #update repeatedly evaluates the caller's block and never returns. In services that store externally derived numeric values in an AtomicReference, this can cause CPU exhaustion or permanent request/job hangs. This vulnerability is fixed in 1.3.7.
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-2026-54904 has been found in concurrent-ruby.
Attackers can target a specific entry point like compare_and_set over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade concurrent-ruby to 1.3.7 or later.
If unsure, ask your IT team or search "concurrent-ruby CVE-2026-54904" on the vendor's site.
CVE-2026-54904 (concurrent-ruby) — CWE-835 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: compare_and_set / false / AtomicReference
Patched: 1.3.7 — 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-835) exists in concurrent-ruby. Attackers reach the vulnerable code path via compare_and_set without authentication.
Check the vendor advisory for the affected versions of concurrent-ruby. Attack surface: compare_and_set / false / AtomicReference.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 1.3.7.
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 'concurrent-ruby' . 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
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1Identify exposure identify
grep -r 'concurrent-ruby' . | 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
concurrent-ruby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 concurrent-ruby to 1.3.7ステージング環境で 1.3.7 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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-54904 ruby-concurrent
- Ubuntu UBUNTU-CVE-2026-54904 ruby-concurrent
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- advisory github.com
- patch github.com
- web github.com
- web github.com
- web cve.org