Out-of-Bounds Read in re2 (CVE-2026-71498)
Summary
Vulnerability in re2 (CVE-2026-71498). Risk of unauthorized operations or information disclosure. Exploitable via re2. Mitigation: upgrade to 1.26.1 or later.
Original description
The description as published by the source.
Summary
re2 infers a character's byte length from its UTF-8 lead byte alone, with no bound on the
bytes actually remaining in the input. Buffer arguments reach the native layer verbatim —
only strings are re-encoded into well-formed UTF-8 — so a Buffer whose last byte is a
multi-byte lead promises continuation bytes that are not there, and the result builders read
up to 3 bytes past the end of the buffer. In replace() and split() those bytes are copied
into the returned Buffer, disclosing adjacent heap memory to JavaScript. The trigger is
deterministic and requires no special heap grooming.
Only Buffer input is affected. String input was never at risk: re-encoding guarantees every
multi-byte sequence is complete.
Root cause
getUtf8CharSize maps a lead byte to a length of 1–4 and never sees the input size:
// lib/wrapped_re2.h
inline size_t getUtf8CharSize(char ch)
{
return ((0xE5000000 >> ((ch >> 3) & 0x1E)) & 3) + 1;
}
Callers then read that many bytes. In the zero-width branch of replace(), the guard proves
only that at least one byte remains:
// lib/replace.cc
else if ((size_t)offset < size)
{
auto sym_size = getUtf8CharSize(data[offset]); // may claim up to 4 bytes
result.append(data + offset, sym_size); // reads data[offset .. offset + 3]
byteIndex = offset + sym_size;
}
offset < size permits offset == size - 1, so a lead byte of 0xF0 makes append read
data[size], `data[s…
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-2026-71498 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: 5.1/10.
What to do: upgrade re2 to 1.26.1 or later.
If unsure, ask your IT team or search "re2 CVE-2026-71498" on the vendor's site.
CVE-2026-71498 (re2) — CWE-125 / CVSS v3 5.1
Attack vector: local / unauthenticated / no user interaction
Attack surface: re2 / Buffer / getUtf8CharSize / append
Patched: 1.26.1 — 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 / Buffer / getUtf8CharSize / append.
Severity: Medium (CVSS 5.1/10). Risk of unauthorized operations or information disclosure.
Update to 1.26.1.
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 1.26.1ステージング環境で 1.26.1 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-2026-71498 node-re2
- Ubuntu UBUNTU-CVE-2026-71498 node-re2
References
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com