CVE-2026-49837
MediumCVSS 5.9Exploitation Probability (EPSS)
Low risk17th percentile - higher than 17% of all known CVEs
Summary
GoBGP, a BGP implementation in Go, prior to version 4.6.0 has a BGP OPEN capability parsing issue where several capability decoders may read from the full remaining capability buffer instead of the slice bounded by the declared CapLen. A malformed BGP OPEN message can cause bytes from a following capability to be interpreted as part of the current one; the most security-relevant case is the 4-octet AS capability, where CapLen == 0 may cause the parser to read bytes from the following capability as the 4-octet AS value. This parsed value may later affect peer AS validation during BGP session establishment. Version 4.6.0 patches the issue.
Risk Assessment
An attacker may influence peer AS validation during BGP session establishment, potentially bypassing checks and establishing sessions improperly.
Recommendation
Update GoBGP to version 4.6.0 or later. Until then, consider restricting accepted BGP peers to trusted addresses.
Other vulnerabilities in GoBGP
See all- CVE-2026-42285High
In version 4.4.0 of GoBGP, an unauthenticated remote BGP peer can trigger a fatal panic by sending a specially crafted BGP UPDATE message. This bug causes the entire GoBGP process to crash, resulting in a complete loss of service availability.
- CVE-2026-41643High
GoBGP, an open source implementation of the BGP protocol in Go, prior to version 4.3.0 has a remote Denial of Service (DoS) vulnerability. A malformed BGP UPDATE message can trigger a runtime error related to an index out of range.
- CVE-2026-41642High
In version 4.3.0 of GoBGP, an open source BGP implementation, a remote Denial of Service (DoS) vulnerability exists due to a nil pointer dereference. A malformed BGP UPDATE message containing an unrecognized Path Attribute marked as 'Well-known' leads to a process crash.
- CVE-2026-37461High
An out-of-bounds read in the ParseIP6Extended function in gobgp v4.3.0 allows attackers to cause a Denial of Service (DoS) by supplying a crafted BGP UPDATE message.
- CVE-2026-49838Medium
GoBGP, a BGP implementation in Go, prior to version 4.7.0 accepts a zero-length AS_PATH during UPDATE decoding and later panics while validating that attribute for a confederation eBGP peer. A malformed UPDATE that should be rejected as an invalid AS_PATH reaches an unchecked p.Value[0] access, allowing a configured confederation eBGP peer to trigger a denial of service. Version 4.7.0 patches the issue.
- CVE-2026-37462High
An integer underflow in the BGPUpdate.DecodeFromBytes function (/bgp/bgp.go) of gobgp v4.3.0 allows attackers to cause a denial of service by sending a crafted BGP UPDATE message.
Original NVD description (English source)
GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. Versions prior to 4.6.0 contain a BGP OPEN capability parsing issue where several concrete capability decoders may parse data from the full remaining capability buffer instead of the slice bounded by the declared capability length, `CapLen`. A malformed BGP OPEN message can cause bytes from a following capability to be interpreted as part of the current capability. The most security-relevant case is the 4-octet AS capability, where a capability with `CapLen == 0` may cause the parser to read bytes from the following capability as the 4-octet AS value. This parsed value may later affect peer AS validation during BGP session establishment. Version 4.6.0 patches the issue.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS