Vulnerability in concurrent-ruby (CVE-2026-54906)
Summary
Vulnerability in concurrent-ruby (CVE-2026-54906). Successful exploitation can lead to full system takeover. Exploitable via release_write_lock. 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::ReadWriteLock#release_write_lock does not verify that the calling thread acquired the write lock. Any thread with access to the lock object can release an active write lock held by another thread. A second writer can then enter its critical section while the first writer is still running. Concurrent::ReadWriteLock#release_read_lock also decrements the shared counter even when no read lock is held. Calling it on a fresh lock changes the counter from 0 to -1, after which normal read acquisition raises Concurrent::ResourceLimitError. This is a synchronization correctness issue in the public Concurrent::ReadWriteLock API. 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-2026-54906 has been found in concurrent-ruby.
Attackers can target a specific entry point like release_write_lock over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 9.8/10.
What to do: upgrade concurrent-ruby to 1.3.7 or later.
If unsure, ask your IT team or search "concurrent-ruby CVE-2026-54906" on the vendor's site.
CVE-2026-54906 (concurrent-ruby) — CWE-414 / CVSS v3 9.8
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: release_write_lock / RUNNING_WRITER / release_read_lock / acquire_read_lock
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-414) exists in concurrent-ruby. Attackers reach the vulnerable code path via release_write_lock without authentication.
Check the vendor advisory for the affected versions of concurrent-ruby. Attack surface: release_write_lock / RUNNING_WRITER / release_read_lock / acquire_read_lock.
Severity: Critical (CVSS 9.8/10). Successful exploitation can lead to full system takeover.
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-2026-54906 ruby-concurrent
- Ubuntu UBUNTU-CVE-2026-54906 ruby-concurrent
References
- advisory github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- web github.com