CVE-2026-48521: envoyproxy envoy · NULL Pointer Dereference
Affects envoyproxy envoySource CVE Database V5
Public exploit available · CVSS 5.9 Medium · fixed in 1.39.1 : patch envoyproxy envoy as a priority.
Data as of 5 Nov 2026, 00:01 UTC
- EPSS
- 0.7% chance of exploitation in 30 days – higher than 54% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- CISA SSVC
- Exploitation
- Proof of concept is public or traded
- Automatable
- Attackers cannot reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-09-21.
- Patch
- Available – fixed in 1.39.1, 1.38.4, 1.37.6 +1
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
t = 0 is the CVE’s publication on cve.org
Disclosed: evidence found.
CVE published 21 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CISA SSVC: proof of concept public
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
Timeline
CVE ID reserved
by GitHub, Inc.
, 123 days before disclosure
CVE published
on cve.org
, t = 0
CISA SSVC assessment
proof of concept public
, 18 minutes after disclosure
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA SSVC, the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.
What to do
Upgrade envoyproxy envoy to 1.39.1, 1.38.4, 1.37.6 or 1.36.10.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| envoyproxyenvoy | Affected
| Fixed in
|
| envoyproxyenvoy | Affected
| Fixed in
|
| envoyproxyenvoy | Affected
| Fixed in
|
| envoyproxyenvoy | Affected
| Fixed in
|
AI-suggested
Upgrade Envoy to version 1.36.10, 1.37.6, 1.38.4, or 1.39.1 or later where this issue is fixed. No other mitigations are specified or required.
Description
CVE-2026-48521 is a NULL pointer dereference vulnerability in Envoy proxy versions prior to 1.36.10, 1.37.6, 1.38.4, and 1.39.1. The flaw occurs in the ProdClusterManagerFactory::allocateConnPool function when selecting an HTTP/3 connection pool without checking if transport_socket_options is null. This can cause an Envoy worker to crash when certain LoadBalancerContext implementations return no transport-socket options and HTTP/3 is enabled.
References
- github.com/envoyproxy/envoy/security/advisories/GHSA-5vff-j9p4-38j3 (opens in a new tab)
- github.com/envoyproxy/envoy/commit/8ef2da8527fcd17388b046c1add4fb47fb5d0868 (opens in a new tab)
- github.com/envoyproxy/envoy/commit/cec4899acf03cf551f28611a5f32385648d95f96 (opens in a new tab)
- github.com/envoyproxy/envoy/commit/e7b4839beef7f43594ce8e94c4563c80db04a8a7 (opens in a new tab)
- github.com/envoyproxy/envoy/commit/f5436f44103fb14cb8ba42a8db0f54a06c98c45a (opens in a new tab)
- github.com/envoyproxy/envoy/releases/tag/v1.36.10 (opens in a new tab)
- github.com/envoyproxy/envoy/releases/tag/v1.37.6 (opens in a new tab)
- github.com/envoyproxy/envoy/releases/tag/v1.38.4 (opens in a new tab)
- github.com/envoyproxy/envoy/releases/tag/v1.39.1 (opens in a new tab)