# CVE-2026-78048: Apache bRPC assertion failure in HPACK decoder

Source: https://junglewise.ai/threats/cve-2026-78048-a-reachable-assertion-flaw-in-the-hpack-header-compression  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-21. Updated: 2026-10-21  
License: CC BY 4.0 with a link back

CVE-2026-78048 · Severity: info · Published 2026-10-21

Apache bRPC is an open-source RPC framework used to build distributed services. A flaw in its HTTP/2 header decompression logic allows a remote attacker to crash a bRPC server by sending specially crafted headers, causing service outages without requiring authentication.

Technologies: [Apache Brpc](https://junglewise.ai/threats/technologies/brpc). Vendors: [Apache](https://junglewise.ai/threats/vendors/apache).

## Quick answers

**Is CVE-2026-78048 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-78048 being exploited in the wild.

**How severe is CVE-2026-78048?** Informational severity, published 21 October 2026.

**Which products and versions are affected?** Apache Brpc < 1.18.0.

**Is there a fix for CVE-2026-78048?** Yes: fixed in 1.18.0. Until then: Restrict HTTP/2 and gRPC traffic to trusted sources only via network-level access controls until bRPC can be upgraded.</anigation>
<parameter name="timeline">[{"kind": "disclosed", "at": "2026-10-21"}] Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-78048 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-78048?** Check whether you run Apache Brpc 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.

## How to fix

- Fixed in 1.18.0

Restrict HTTP/2 and gRPC traffic to trusted sources only via network-level access controls until bRPC can be upgraded.</anigation>
<parameter name="timeline">[{"kind": "disclosed", "at": "2026-10-21"}]

## Technical details

The HPACK decoder in src/brpc/details/hpack.cpp incorrectly sizes the dynamic table ring buffer based on a 34-byte minimum entry assumption, contradicting RFC 7541's 33-byte minimum. An attacker can add 121 minimal entries to the 4096-byte default table (consuming ~3993 bytes), triggering a buffer-full CHECK() assertion on the 121st header that aborts the process. The vulnerability is exploitable remotely over HTTP/2 or gRPC without authentication.

## Affected products

- Apache bRPC < 1.18.0

## Related threats

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- [Apache bRPC HTTP request/response smuggling in bundled parser](https://junglewise.ai/threats/cve-2026-86146-inconsistent-interpretation-of-http-requests-http-request)