{"id":18851,"date":"2026-03-31T11:42:10","date_gmt":"2026-03-31T11:42:10","guid":{"rendered":"https:\/\/cryptoted.net\/index.php\/2026\/03\/31\/security-alert-implementation-of-blockhash-instruction-in-c-and-go-clients-can-potentially-cause-consensus-issue-fixed-please-update\/"},"modified":"2026-03-31T11:42:10","modified_gmt":"2026-03-31T11:42:10","slug":"security-alert-implementation-of-blockhash-instruction-in-c-and-go-clients-can-potentially-cause-consensus-issue-fixed-please-update","status":"publish","type":"post","link":"https:\/\/cryptoted.net\/index.php\/2026\/03\/31\/security-alert-implementation-of-blockhash-instruction-in-c-and-go-clients-can-potentially-cause-consensus-issue-fixed-please-update\/","title":{"rendered":"Security alert [Implementation of BLOCKHASH instruction in C++ and Go clients can potentially cause consensus issue \u2013 Fixed. Please update.]"},"content":{"rendered":"


\n<\/p>\n

\n

Summary: <\/b>Erroneous implementation of BLOCKHASH can trigger a chain reorganisation leading to consensus problems<\/p>\n

Affected configurations: <\/b>All geth versions up to 1.1.3 and 1.2.2. All eth versions prior to 1.0.0.<\/p>\n

Likelihood: <\/b>Low<\/p>\n

Severity: <\/b>Medium<\/p>\n

Impact: <\/b>Medium<\/p>\n

Details:<\/b> Both C++ (eth) and Go (geth) clients have an erroneous implementation of an edge case in the Ethereum virtual machine, specifically which chain the BLOCKHASH instruction uses for retrieving a block hash. This edge case is very unlikely to happen on a live network as it would only be triggered in certain types of chain reorganisations (a contract executing BLOCKHASH(N – 1) where N is the head of a non-canonical subchain that is not-yet reorganised to become the canonical (best\/longest) chain but will be after the block is processed).<\/p>\n

pyethereum is unaffected.<\/p>\n

Effects on expected chain reorganisation depth: <\/b>none<\/p>\n

Remedial action taken by Ethereum<\/b>: Provision of hotfixes as below.<\/p>\n

<\/g><\/svg><\/a>Geth:<\/strong><\/h3>\n

PPA<\/strong>: sudo apt-get update then sudo apt-get upgrade<\/p>\n

Brew<\/strong>: brew update then brew reinstall ethereum<\/p>\n

Windows<\/strong>: download the updated binary from https:\/\/github.com\/ethereum\/go-ethereum\/releases\/tag\/v1.2.3<\/a><\/p>\n

Building from source:<\/strong><\/p>\n

\n
git fetch origin && git checkout origin\/master<\/pre>\n<\/div>\n
<\/g><\/svg><\/a>Eth:<\/strong><\/h3>\n
PPA<\/strong>: https:\/\/gavofyork.gitbooks.io\/turboethereum\/content\/chapter1.html<\/a>\n<\/div>\n

\n
Source link <\/a><\/p>\n","protected":false},"excerpt":{"rendered":"
Summary: Erroneous implementation of BLOCKHASH can trigger a chain reorganisation leading to consensus problems Affected configurations: All geth versions up to 1.1.3 and 1.2.2. All eth versions prior to 1.0.0. Likelihood: Low Severity: Medium Impact: Medium Details: Both C++ (eth) and Go (geth) clients have an erroneous implementation of an edge case in the Ethereum […]<\/p>\n","protected":false},"author":6,"featured_media":18498,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"tdm_status":"","tdm_grid_status":"","footnotes":""},"categories":[24],"tags":[],"kronos_expire_date":[],"class_list":["post-18851","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-ethereum"],"_links":{"self":[{"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/posts\/18851","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/comments?post=18851"}],"version-history":[{"count":0,"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/posts\/18851\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/media\/18498"}],"wp:attachment":[{"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/media?parent=18851"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/categories?post=18851"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/tags?post=18851"},{"taxonomy":"kronos_expire_date","embeddable":true,"href":"https:\/\/cryptoted.net\/index.php\/wp-json\/wp\/v2\/kronos_expire_date?post=18851"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}