GHSA-9wh6-9hq7-9688 CVE-2026-82407 GO-2026-6586
Klever-Go: Validator registration accepts an unvalidated BLS public key → consensus liveness DoS
- Severity
- 0.0 / 10
- High · CVSS 4.0
- Exploit chance (EPSS)
- 0.47%
- Chance of exploitation in the next 30 days. Higher than 40.36% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-20 Improper Input Validation
- Fix
1.7.20- Upgrade github.com/klever-io/klever-go to this version or later
Description
Location: core/kapp/validators/validators.go:201 (Register), (genesis/checking/nodesSetupChecker.go:73). core/consensus/slot/bls/subslotStartSlot.go:165 core/consensus/.../headerSignatureVerify.go:123 (Create(...)).
Description
Klever uses a BDN (Boneh-Drijvers-Neven) BLS multi-signature over BLS12-381 to finalize blocks (crypto/signing/mcl/multisig/bls.go, herumi/bls-go-binary). The library is initialized with only bls.Init(bls.BLS12_381) and no order-verification flags, so Deserialize does not enforce prime-order-subgroup membership subgroup safety relies on explicit IsValidOrder() calls in the wrappers.
Runtime validator registration (validators.Register) stores the submitted 96-byte BLSPublicKey via SetBLSPublicKey with no curve check, no subgroup check, and no proof-of-possession (CreateValidatorContract carries the key but no signature proving key ownership; grep confirms no proofOfPossession/VerifyProof/BLSSignature verification anywhere in core/kapp/validators/). CheckPublicKeyValid — which does IsValid && IsValidOrder && !IsZero — runs only at genesis, not on runtime registration/update.
POC
Attack:
(1) stake the minimum to register a validator, submitting a 96-byte BLSPublicKey that is not a valid G2 point (arbitrary bytes). Registration succeeds.
(2) Once the validator is eligible and selected into a consensus group, every in-group node including the honest leader (group[0]) calls MultiSigner().Reset(groupPubKeys, selfIndex) at slot start, which deserializes all group keys via PublicKeyFromByteArray → herumi Deserialize deterministically fails on the malformed key → SetSlotCanceled(true). The verify side (Create(consensusPubKeys)) fails identically. No block is produced for that round.
Impact
Every consensus round whose group contains the malformed-key validator is a missed slot. One eligible bad-key validator poisons roughly a groupSize / eligibleSet fraction of rounds → sustained liveness degradation. Where the consensus group equals the eligible set (small or early-stage networks), this is a full chain halt. Cost is the minimum validator stake, permissionless, and repeatable; no fork flag gates the missing validation.
Rated High (Byzantine liveness; Critical on small validator sets). The severity scales down to a fractional missed-slot / throughput-degradation attack on a large validator set where the bad validator is only occasionally in the active group.
Recommendation
Enforce CheckPublicKeyValid (curve + prime-order subgroup + non-zero) on the submitted BLS key at runtime validator registration and config-update, and ideally require a proof-of-possession (a BLS signature over the validator's own key/identity) at registration to prove key ownership and well-formedness. Gate the stricter validation behind an epoch fork flag for reprocessing consistency.
Affected versions
Go
| Package | Vulnerable | Fixed in |
|---|---|---|
| github.com/klever-io/klever-go | < 1.7.20 |
1.7.20 |
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
github.com/klever-io/klever-go Go → 1.7.20
- go
go get github.com/klever-io/klever-go@v1.7.20 && go mod tidy
Severity breakdown
CVSS 4.0 0.0
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H
- Attack vector
- Network
- Attack complexity
- Low
- Attack requirements
- Present
- Privileges required
- Low
- User interaction
- None
- Confidentiality (vulnerable system)
- None
- Integrity (vulnerable system)
- None
- Availability (vulnerable system)
- High
- Confidentiality (subsequent systems)
- None
- Integrity (subsequent systems)
- None
- Availability (subsequent systems)
- High
Weakness
CWE-20: Improper Input Validation
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
How to prevent it
- Architecture and Design: Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build "recognizers" for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of allowing parser code to be scattered throughout the program, where it could be subject to errors or inconsistencies that create weaknesses. [REF-1109] [REF-1110] [REF-1111]
- Architecture and Design: Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
- Architecture and Design, Implementation: Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.
- Implementation: Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does. When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue." Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
- Architecture and Design: For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server. Even though client-side checks provide minimal benefits with respect to server-side security, they are still useful. First, they can support intrusion detection. If the server receives input that should have been rejected by the client, then it may be an indication of an attack. Second, client-side error-checking can provide helpful feedback to the user about the expectations for valid input. Third, there may be a reduction in server-side processing time for accidental input errors, although this is typically a small savings.
- Implementation: When your application combines data from multiple sources, perform the validation after the sources have been combined. The individual data elements may pass the validation step but violate the intended restrictions after they have been combined.
- Implementation: Be especially careful to validate all input when invoking code that crosses language boundaries, such as from an interpreted language to native code. This could create an unexpected interaction between the language boundaries. Ensure that you are not violating any of the expectations of the language with which you are interfacing. For example, even though Java may not be susceptible to buffer overflows, providing a large argument in a call to native code might trigger an overflow.
- Implementation: Directly convert your input type into the expected data type, such as using a conversion function that translates a string into a number. After converting to the expected data type, ensure that the input's values fall within the expected range of allowable values and that multi-field consistencies are maintained.
- Implementation: Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180, CWE-181). Make sure that your application does not inadvertently decode the same input twice (CWE-174). Such errors could be used to bypass allowlist schemes by introducing dangerous inputs after they have been checked. Use libraries such as the OWASP ESAPI Canonicalization control. Consider performing repeated canonicalization until your input does not change any more. This will avoid double-decoding and similar scenarios, but it might inadvertently modify inputs that are allowed to contain properly-encoded dangerous content.
- Implementation: When exchanging data between components, ensure that both components are using the same character encoding. Ensure that the proper encoding is applied at each interface. Explicitly set the encoding you are using whenever the protocol allows you to do so.
References
Packages
Other links
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-7c7c-373r-gfjj Klever-Go: Elasticsearch bulk / painless injection via on-chain account name -> explorer/indexer data forgery | High | Also affects github.com/klever-io/klever-go |
| GHSA-26r5-4mm2-px5c Klever-Go: Zombie-order theft: `Buy` missing `IsClaimed` guard in native marketplace | High | Also affects github.com/klever-io/klever-go |
| GHSA-97cv-x867-6xhm Klever-Go Account takeover: `kleverUpdateAccountPermission` authorizes on attacker-controlled `RecipientAddr` instead of the authenticated caller | High | Also affects github.com/klever-io/klever-go |
| GHSA-4fwh-wrm6-97xm Klever-Go: Unauthenticated WebSocket /subscribe: no read-size limit, no connection cap, permissive origin -> remote node memory/goroutine exhaustion (DoS) | High | Also affects github.com/klever-io/klever-go |
| GHSA-9v8p-frvj-2pcm Klever-Go: /log controls global node logging | High | Also affects github.com/klever-io/klever-go |
| GHSA-mrpp-v6pg-p54x klever-go: SFT add-quantity `int64` overflow bypasses a finite per-nonce MaxSupply | High | Also affects github.com/klever-io/klever-go |
| GHSA-v358-wf77-39xv klever-go: Percentage-transfer royalty skips the source debit at exactly-100% splits | High | Also affects github.com/klever-io/klever-go |
| GHSA-cgc5-v3f2-8m2v Klever: Integer overflow in split-royalty validation enables unbounded minting of KLV (native token) | Critical | Also affects github.com/klever-io/klever-go |
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