Safe is a multi-signature smart contract wallet designed for collective management of digital assets. The wallet requires a predefined threshold of owner signatures before any transaction can be executed. To enhance functionality, Safe supports extensions through modules and fallback handlers.<\/p>\n
Safe engaged Ackee Blockchain Security to perform a security review of Safe Smart Account with a total time donation of 20 engineering days in a period between April 14 and May 12, 2025. 6 engineering days were dedicated to manually-guided differential fuzzing using the Wake<\/span><\/a> testing framework.<\/p>\n A second, fix review was performed between May 20 and May 27, 2025.<\/p>\n We began our audit with a manual review of the codebase in parallel with manually-guided fuzzing using the Wake<\/span><\/a> testing framework. For static analysis, we utilized Wake<\/span><\/a> vulnerability and code quality detectors.<\/p>\n During the review, we focused on ensuring that:<\/p>\n The audit was performed on the commit The second, fix review was performed on commit The classification of a security finding is determined by two ratings: <\/span>impact<\/b> and <\/span>likelihood<\/b>. This two-dimensional classification helps clarify the severity of individual issues. Issues which would be rated as <\/span>medium<\/span><\/i> severity, but which would be likely discovered only by the team, are typically decreased by the likelihood factor to the W<\/em><\/span>arning<\/span><\/i> or I<\/em><\/span>nformational<\/span><\/i> severity ratings.<\/span><\/p>\n Our review resulted in 19 findings, ranging from Info to Medium severity. The most severe finding M1<\/span> was discovered through manually-guided fuzzing<\/strong>. The issue revealed a possibility of a front-running attack where an attacker could deploy a new Safe on behalf of a user without executing the intended callback. The issue sits in The M1 issue was found in already-deployed contracts of version 1.4.1 (and lower) across all supported chains.<\/span> Ackee Blockchain Security initiated an immediate responsible disclosure over a secure channel as soon as the finding was identified to mitigate any possible risk. The validity of the finding was promptly acknowledged by the Safe team, according to whom the issue has never been exploited. A fix is scheduled for Safe’s upcoming v1.5.0 release.<\/span><\/p>\n The code is well documented, and possible caveats and security considerations are explained. There is room for improvements in terms of user experience (W1<\/span>, W7<\/span>, I4<\/span>, I5<\/span>). The reviewed version of Safe is incompatible with EIP-7702<\/span> smart accounts.<\/p>\n No critical severity issues were found.<\/p>\n No high severity issues were found.<\/p>\n M1: Front-running attack can bypass callback execution during Safe deployment<\/p>\n L1: L2: Strict calldata check on W1: Misleading event emissions<\/p>\n W2: Use of precomputed W3: Scratch space assumed zeroed out<\/p>\n W4: Safe W5: W6: Locked tokens possibility<\/p>\n W7: I1: Documentation issues<\/p>\n I2: Unnecessary typecasts to I3: Code optimizations<\/p>\n I4: Factory I5: No view function for I6: I7: Missing L2-specific variant of I8: Interface type used for parameter that accepts zero address<\/p>\n I9: Owners of a Safe have full control over the Safe. Any attached modules must be trusted, as they can execute arbitrary transactions from the Safe. Attached fallback handler must be trusted as it can verify ERC-1271 <\/span>signatures on behalf of the Safe.<\/p>\n Safe proxy factory may be trusted to provide a front-running protection when used correctly. I.e. it is guaranteed that a precomputed Safe address will belong to the intended owners as long as the Safe setup is performed as an initialization step of the proxy deployment.<\/p>\n Ackee Blockchain Security recommends Safe to:<\/p>\n document that the Safe account is not fully compatible with EIP-7702<\/span>;<\/p>\n<\/li>\n clearly mark files under contracts\/examples<\/span> as non-production code;<\/p>\n<\/li>\n document functionalities that are not supported by address all identified issues.<\/p>\n<\/li>\n<\/ul>\n Ackee Blockchain Security<\/a>\u2019s full Safe audit report can be found here<\/a><\/b>.<\/b><\/p>\n We are always delighted to work with Safe’s world-class team and look forward to auditing them again in the future.<\/p>\n","protected":false},"excerpt":{"rendered":" Safe is a multi-signature smart contract wallet designed for collective management of digital assets. The wallet requires a predefined threshold of owner signatures before any transaction can be executed. To enhance functionality, Safe supports extensions through modules and fallback handlers. Safe engaged Ackee Blockchain Security to perform a security review of Safe Smart Account with a total time donation of 20 engineering…<\/p>\n","protected":false},"author":30,"featured_media":1057,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[20,10,103],"tags":[21,89,24,101],"class_list":["post-1055","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-audits","category-ethereum","category-wake","tag-audit","tag-audit-summary","tag-ethereum","tag-safe"],"aioseo_notices":[],"featured_image_src":"https:\/\/ackee.xyz\/blog\/wp-content\/uploads\/2025\/06\/Safe-blog-600x400.png","featured_image_src_square":"https:\/\/ackee.xyz\/blog\/wp-content\/uploads\/2025\/06\/Safe-blog-600x600.png","author_info":{"display_name":"Tom\u00e1\u0161 Kova\u0159\u00edk","author_link":"https:\/\/ackee.xyz\/blog\/author\/tomas-kovarik\/"},"_links":{"self":[{"href":"https:\/\/ackee.xyz\/blog\/wp-json\/wp\/v2\/posts\/1055","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ackee.xyz\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ackee.xyz\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ackee.xyz\/blog\/wp-json\/wp\/v2\/users\/30"}],"replies":[{"embeddable":true,"href":"https:\/\/ackee.xyz\/blog\/wp-json\/wp\/v2\/comments?post=1055"}],"version-history":[{"count":0,"href":"https:\/\/ackee.xyz\/blog\/wp-json\/wp\/v2\/posts\/1055\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/ackee.xyz\/blog\/wp-json\/wp\/v2\/media\/1057"}],"wp:attachment":[{"href":"https:\/\/ackee.xyz\/blog\/wp-json\/wp\/v2\/media?parent=1055"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ackee.xyz\/blog\/wp-json\/wp\/v2\/categories?post=1055"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ackee.xyz\/blog\/wp-json\/wp\/v2\/tags?post=1055"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}METHODOLOGY<\/span><\/h2>\n
\n
CompatibilityFallbackHandler<\/code> contract; and<\/span><\/li>\nSCOPE<\/span><\/h2>\n
b115c4c<\/code>\u00a0in the safe-smart-account<\/span><\/a> repository. The scope of the audit included all Solidity files in the contracts<\/code> directory, excluding contracts\/examples<\/code><\/span> and contracts\/test<\/code><\/span>.\u00a0<\/span><\/p>\nd89d156<\/code><\/span> was initially used as the target commit, but it was later updated to include changes in the CompatibilityFallbackHandler<\/code>\u00a0contract.<\/p>\n5d26505<\/code> in the safe-smart-account<\/a> repository.<\/p>\nFINDINGS<\/span><\/h2>\n
SafeProxyFactory<\/code>, not the Safe account itself; it involves the (now-removed) <\/span>createProxyWithCallback<\/span> method, and no existing Safes are affected. <\/span>The issue was not identified by earlier formal-verification checks and previous audits.<\/b><\/p>\nCritical severity<\/span><\/h3>\n
High severity<\/span><\/h3>\n
Medium severity<\/span><\/h3>\n
Low severity<\/span><\/h3>\n
CompatibilityFallbackHandler<\/code> does not provide full compatibility<\/p>\nmasterCopy<\/code>\u00a0call<\/span><\/p>\nWarning severity<\/span><\/h3>\n
msg.data<\/code><\/p>\nsetup<\/code> may emit outdated information<\/p>\nonlyNonceZero<\/code> check can\u00a0<\/span>be bypassed<\/p>\nProxyCreationL2<\/code> nonce value is not user-given argument<\/p>\nInformational severity<\/span><\/h3>\n
payable<\/code><\/p>\ninitializer<\/code> error not propagated<\/p>\nFallbackManager<\/code> handler address<\/p>\nSafeStorage<\/code> can be defined as abstract<\/p>\ncreateChainSpecificProxyWithNonce<\/code><\/p>\nChangedThreshold<\/code> event is emitted unconditionally<\/p>\nTRUST MODEL<\/span><\/h2>\n
CONCLUSION<\/span><\/h2>\n
\n
CompatibilityFallbackHandler<\/code>;\u00a0and<\/span><\/p>\n<\/li>\n