Besu 26.11.0 upgrades Vert.x to 5.2.2 to fix October 2026 Vert.x advisories, including HTTP/1.x request smuggling
Besu 26.11.0 upgrades Vert.x from 5.1.6 to 5.2.2, fixing the Vert.x advisories published in October 2026 (HTTP/1.x request smuggling, unbounded allocation for compressed WebSocket frames, incomplete HTTP client SSL context cache key). Operators should upgrade.
Vuln-watch · relayed from an upstream security release; see Source & attribution below
Summary
Besu 26.11.0 (released 2026-11-02) upgrades its Vert.x dependency from 5.1.6 to 5.2.2, which per the release notes fixes the Vert.x advisories published in October 2026 (#11770). The release also changes some defaults and RPC behaviour.
Affected
- Besu (hyperledger/besu, now besu-eth/besu) versions before 26.11.0 bundling Vert.x 5.1.6
- Fixed in 26.11.0
Impact
The release notes name the fixed Vert.x issue types as HTTP/1.x request smuggling, unbounded allocation for compressed WebSocket frames, and an incomplete HTTP client SSL context cache key. No CVE/GHSA identifiers are given in the notes and no exploitation in the wild is reported.
Recommended actions
- Upgrade Besu to 26.11.0 or later
- Review breaking changes: --Xpos-block-finalization-timeout-ms default changes from 800 to 0 (#11774); eth_getProof follows execution-apis leading-zero/error rules (#11668); eth_simulateV1 rejects unknown account overrides (#11695)
- Avoid exposing JSON-RPC/WebSocket endpoints to untrusted networks
Source & attribution
This 0xCERT advisory relays the Besu 26.11.0 release notes: https://github.com/besu-eth/besu/releases/tag/26.11.0. Details may change; refer to the upstream project for the authoritative record and any follow-up security advisories.
OpenPGP-signed. The signed text of this advisory verifies against the 0xCERT key CCC7 D9EC 9415 723D.
Published 2026-11-02 · last updated 2026-11-02
curl -s https://www.0xcert.com/pgp.asc | gpg --import && curl -s https://www.0xcert.com/advisory/0xCERT-2026-0300/signed.txt | gpg --verify