# CVE-2026-37459: FRRouting integer underflow in BGP UPDATE message parsing

Source: https://junglewise.ai/threats/cve-2026-37459-frrouting-integer-underflow-in-bgp-update-message-parsing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-04. Updated: 2026-06-30  
License: CC BY 4.0 with a link back

CVE-2026-37459 · Severity: high · CVSS 7.5 · Published 2026-05-04

FRRouting (FRR) is an open-source software suite used to manage network routing protocols like BGP on Linux and Unix systems. A vulnerability in how it handles certain network update messages allows an attacker to crash the routing service remotely. This can lead to a total loss of network connectivity for the affected systems, disrupting business operations and data flow.

Technologies: [Frrouting](https://junglewise.ai/threats/technologies/frrouting), [Red Hat Enterprise Linux 10](https://junglewise.ai/threats/technologies/enterprise-linux-10), [Red Hat Enterprise Linux 8](https://junglewise.ai/threats/technologies/enterprise-linux-8), [Red Hat Enterprise Linux 9](https://junglewise.ai/threats/technologies/enterprise-linux-9). Vendors: [Frrouting](https://junglewise.ai/threats/vendors/frrouting), [Red Hat](https://junglewise.ai/threats/vendors/red-hat).

## Quick answers

**Is CVE-2026-37459 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-37459 being exploited in the wild.

**How severe is CVE-2026-37459?** High severity, with a CVSS score of 7.5, published 4 May 2026.

**Which products and versions are affected?** Frrouting stable/10.0 to stable/10.6.

**Is there a fix for CVE-2026-37459?** A patch was published on 2026-06-08: Red Hat released security updates (RHSA-2026:24347, RHSA-2026:24370) Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-37459 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-37459?** Check whether you run Frrouting, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8 or one of the others listed at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

An integer underflow vulnerability exists in the BGP daemon (bgpd) of FRRouting (FRR) within the `bgp_attr_nhc` function in `bgp_attr.c`. The root cause is an insufficient length check when parsing Next Hop Capability (NHC) Type-Length-Value (TLV) structures; specifically, the code fails to account for the TLV header size when validating the remaining stream length. A remote, unauthenticated attacker can exploit this by sending a specially crafted BGP UPDATE message, leading to uncontrolled resource consumption or a process crash (Denial of Service). The issue is addressed in the FRR source code by ensuring the remaining length is sufficient to cover both the TLV value and the header. Patches are available via FRR commits and downstream vendor updates from Red Hat.

## Affected products

- FRRouting FRRouting stable/10.0 to stable/10.6
- Red Hat Red Hat Enterprise Linux 8
- Red Hat Red Hat Enterprise Linux 9
- Red Hat Red Hat Enterprise Linux 10

## Timeline

- 2026-05-04: advisory: Initial NVD publication date
- 2026-05-04: other: Upstream patch committed to GitHub
- 2026-06-08: patched: Red Hat released security updates (RHSA-2026:24347, RHSA-2026:24370)

## References

- [https://github.com/FRRouting/frr/commit/693a2e02687cdc9d16501275e05136edea9650d9](https://github.com/FRRouting/frr/commit/693a2e02687cdc9d16501275e05136edea9650d9)
- [https://access.redhat.com/errata/RHSA-2026:24347](https://access.redhat.com/errata/RHSA-2026:24347)
- [https://access.redhat.com/errata/RHSA-2026:24370](https://access.redhat.com/errata/RHSA-2026:24370)
- [https://access.redhat.com/security/cve/CVE-2026-37459](https://access.redhat.com/security/cve/CVE-2026-37459)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2466513](https://bugzilla.redhat.com/show_bug.cgi?id=2466513)
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-37459.json](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-37459.json)

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