Out-of-Bounds Read in re2 (CVE-2026-67550)
Summary
Vulnerability in re2 (CVE-2026-67550). Risk of unauthorized operations or information disclosure. Exploitable via re2. Mitigation: upgrade to 1.25.1 or later.
Original description
The description as published by the source.
Summary
re2 validates the user-settable lastIndex against the subject's UTF-8 byte length but then uses it as a UTF-16 code-unit count to walk the subject buffer, with no bounds check. For any non-ASCII subject, the byte length is larger than the true character count, so a lastIndex between those two values passes validation while pointing past the end of the buffer. The subsequent walk reads out of bounds. With a large subject the read marches into unmapped memory and the process dies with SIGABRT/SIGSEGV — an uncatchable crash (try/catch cannot stop it), i.e. a denial of service for any worker/process that runs the match. In some cases the out-of-bounds bytes are copied into the returned value (a bounded, best-effort heap information leak).
Root cause
The subject wrapper stores the UTF-8 byte length in StrVal::length:
lib/addon.cc:200auto argLength = utf8Length(s, isolate);— UTF-8 byte countlib/addon.cc:209lastStringValue.reset(buffer, argSize, argLength, startFrom, false, isAscii);
setIndex then validates the (UTF-16) lastIndex against that byte length and walks the buffer by character count:
// lib/addon.cc:229
void StrVal::setIndex(size_t newIndex) {
isValidIndex = newIndex <= length; // length == UTF-8 BYTE length, not UTF-16 length
if (!isValidIndex) { index = newIndex; byteIndex = 0; return; }
...
// addon.cc:263
byteIndex = index < newIndex
? getUtf16PositionByCounter(d…
Source: NIST National Vulnerability Database 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-2026-67550 has been found in re2.
Attackers can target a specific entry point like re2 over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.7/10.
What to do: upgrade re2 to 1.25.1 or later.
If unsure, ask your IT team or search "re2 CVE-2026-67550" on the vendor's site.
CVE-2026-67550 (re2) — CWE-125 / CVSS v3 5.7
Attack vector: local / unauthenticated / no user interaction
Attack surface: re2 / lastIndex / setIndex / getUtf16PositionByCounter
Patched: 1.25.1 — 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.
Out-of-bounds read (CWE-125) exists in re2. Attackers reach the vulnerable code path via re2 without authentication.
Check the vendor advisory for the affected versions of re2. Attack surface: re2 / lastIndex / setIndex / getUtf16PositionByCounter.
Severity: Medium (CVSS 5.7/10). Risk of unauthorized operations or information disclosure.
Update to 1.25.1.
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 're2' . 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 're2' . | 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
re2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 re2 to 1.25.1ステージング環境で 1.25.1 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-2026-67550 node-re2
- Ubuntu UBUNTU-CVE-2026-67550 node-re2
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com