CVE-2026-129456

frr: bgpd use-after-free of Tunnel Encapsulation sub-TLVs after a malformed attribute length from a peer

High 7.7

Description

In FRRouting, bgpd accepts a Tunnel Encapsulation attribute (type 23) whose outer TLV length does not match the length of the attribute: the mismatch is only logged and the attribute is processed anyway. A BGP neighbor can send UPDATE messages carrying such an attribute that put the reference count of the attribute's interned sub-TLV chain out of balance, so that the chain is freed while routes stored by bgpd (Adj-RIB-In entries and RIB paths) still point to it. When those routes are later replaced, withdrawn or cleared, for example when the session goes down, bgpd reads the freed memory, decrements a reference count inside it and frees it a second time. In the reporter's build without AddressSanitizer this ended in an assertion failure in bgpd's memory accounting, aborting bgpd and dropping all BGP sessions on the router, and the neighbor can repeat it each time bgpd restarts. Because freed heap memory is written to and freed again, consequences beyond a crash cannot be ruled out. An established BGP session is required. bgpd processes attribute 23 from every neighbor, including eBGP neighbors, unless it is explicitly discarded, although RFC 9012 requires it to be filtered on eBGP sessions by default. The issue was reproduced with "soft-reconfiguration inbound" configured for the neighbor, and the reporter observed that the crash does not occur on every attempt.

Key facts

Published: 14 Nov 2026
Last changed: 14 Nov 2026
Assigned by: NetDEF
EPSS: 0.267% likely to be exploited in the next 30 days, higher than 19.022% of CVEs (scores for 15 Nov 2026)

Severity scores

Each score is shown as its source gave it. They are not averaged or merged.

7.7CVSS 4.0, Highfrom the CNA (NetDEF)CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:L/AU:N/R:A

What to do

Configure "neighbor <neighbor> path-attribute discard 23" (or "neighbor <neighbor> path-attribute treat-as-withdraw 23") for neighbors that are not expected to send the Tunnel Encapsulation attribute, in particular all eBGP neighbors. bgpd then skips the attribute without parsing it.CNA workaround statement

Historical context and remediation

This reference retains the original CVE publication date. A recent record update does not mean a new attack occurred.

No separately sourced impact summary is available on this page yet. Consult the description, version data and dated exploitation evidence.

Version statuses below come from the CNA. An “unaffected” version is not necessarily a currently supported release or proof of a patch date. EPSS is a dated risk estimate, not a count of historical attacks.

Read the original CVE record.

Affected products

Vendor	Product	Versions
frrouting	frrouting	Default status: unaffected f4c89855b594d4b32bb3610537703215c978440e up to but excluding * (affected); at 1238ac4a06e5c23595e8bf626856f297d0c302a2 unaffected 10.4.0 up to but excluding 10.4.4 (affected) 10.5.0 up to but excluding 10.5.4 (affected)