GoBGP: Remote Denial of Service (Panic) in UpdatePathAttrs4ByteAs via Malformed BGP UPDATE

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. Prior to version 4.3.0, a remote Denial of Service (DoS) vulnerability exists in GoBGP where a malformed BGP UPDATE message can trigger a runtime error: index out of range panic. This occurs during the processing of 4-byte AS attributes when the message structure causes an internal slice index shift that is not properly handled. This issue has been patched in version 4.3.0.

Source published

7 May 2026 11:53:23 UTC

Source modified

7 May 2026 13:39:04 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. Prior to version 4.3.0, a remote Denial of Service (DoS) vulnerability exists in GoBGP where a malformed BGP UPDATE message can trigger a runtime error: index out of range panic. This occurs during the processing of 4-byte AS attributes when the message structure causes an internal slice index shift that is not properly handled. This issue has been patched in version 4.3.0.

Source published

May 7, 2026, 11:53:23 AM (timezone not stated)

Source modified

May 7, 2026, 1:39:04 PM (timezone not stated)

Observed here

28 Oct 2026 05:10:30 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

GoBGP is an open source Border Gateway Protocol (BGP) implementation in the Go Programming Language. Prior to version 4.3.0, a remote Denial of Service (DoS) vulnerability exists in GoBGP where a malformed BGP UPDATE message can trigger a runtime error: index out of range panic. This occurs during the processing of 4-byte AS attributes when the message structure causes an internal slice index shift that is not properly handled. This issue has been patched in version 4.3.0.

Source published

7 May 2026 12:16:17 UTC

Source modified

26 Oct 2026 21:10:00 UTC

Observed here

27 Oct 2026 10:10:19 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

### Summary A remote Denial of Service (DoS) vulnerability exists in GoBGP where a malformed BGP UPDATE message can trigger a runtime error: index out of range panic. This occurs during the processing of 4-byte AS attributes when the message structure causes an internal slice index shift that is not properly handled. ### Details The vulnerability is located in internal/pkg/table/message.go within the UpdatePathAttrs4ByteAs function. When GoBGP processes a BGP UPDATE message containing both an AS_PATH and an AS4_PATH attribute, it attempts to merge or validate them to support 4-byte AS numbers. If the attributes are ordered such that AS4_PATH (Type 17) appears before AS_PATH (Type 2), and the AS4_PATH is deemed invalid/malformed, the code attempts to remove the AS4_PATH attribute from the msg.PathAttributes slice. It appears the crash happens due to an index shift in msg.PathAttributes: ``` #GoBGP v4.2.0 // Line 112: If AS4_PATH precedes AS_PATH, the deletion causes all subsequent attributes to shift left. msg.PathAttributes = append(msg.PathAttributes[:as4AttrPos], msg.PathAttributes[as4AttrPos+1:]...) // Line 206: The stale asAttrPos index is used here. //The function continues to use the stale index (asAttrPos) to update the AS_PATH. Since the slice length has decreased, accessing the old index leads to a panic. msg.PathAttributes[asAttrPos] = bgp.NewPathAttributeAsPath(newIntfParams) ``` This deletion causes all subsequent attributes in the slice to shift left by one position. However, the function continues to use the original asAttrPos index (calculated before the deletion) to access or modify the AS_PATH attribute later at [Line 206](https://www.google.com/search?q=https://github.com/osrg/gobgp/blob/v4.2.0/internal/pkg/table/message.go%23L206). Because the slice is now shorter, the "stale" index points out of bounds, triggering a panic and crashing the entire GoBGP process. ### PoC Environment: * GoBGP version: 4.2.0 Configuration: Passive peering enabled. Reproduction Steps: Configure GoBGP with a neighbor (e.g., 192.168.31.195). Send a specially crafted BGP UPDATE hex payload: ``` ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff 00 22 02 00 00 # Withdrawn Routes Length 00 0b # Total Path Attribute Length 40 11 01 02 # AS4_PATH (Type 17, Len 1, Val 02) - Triggers the bug 40 02 04 ff ff de ad # AS_PATH (Type 2, Len 4) ``` The GoBGP process will immediately crash with: panic: runtime error: index out of range [1] with length 1. ### Impact Vulnerability Type: Remote Denial of Service (DoS). Impacted Users: Any GoBGP deployment (v4.2.0 and earlier) that accepts BGP UPDATE messages from peers. Since this crash occurs in the FSM (Finite State Machine) handling loop, a single malicious peer or a malformed route propagated through a transit provider can consistently crash the BGP daemon, leading to a complete loss of routing capabilities.

Source published

29 Apr 2026 20:44:04 UTC

Source modified

24 Jul 2026 19:11:49 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH

GoBGP: Remote Denial of Service (Panic) in UpdatePathAttrs4ByteAs via Malformed BGP UPDATE in github.com/osrg/gobgp

Source published

24 Jul 2026 18:35:55 UTC

Source modified

24 Jul 2026 19:00:21 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.