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VulnerabilityPublished

CVE-2026-48521: envoyproxy envoy · NULL Pointer Dereference

Affects envoyproxy envoySource CVE Database V5

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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

CVSS 3.1 base score
5.9Medium
How severe the flaw is on the 0–10 CVSS scale.
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:H

Exploitation evidence

t = 0 is the CVE’s publication on cve.org

  1. Disclosed: evidence found.

    CVE published 21 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    CISA SSVC: proof of concept public

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

Timeline

  1. CVE ID reserved

    by GitHub, Inc.

    , 123 days before disclosure

  2. CVE published

    on cve.org

    , t = 0

  3. 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

ProductAffectedFixed in
envoyproxyenvoyAffected
  • >=1.39.0 <1.39.1
Fixed in
  • 1.39.1
envoyproxyenvoyAffected
  • >=1.38.0 <1.38.4
Fixed in
  • 1.38.4
envoyproxyenvoyAffected
  • >=1.37.0 <1.37.6
Fixed in
  • 1.37.6
envoyproxyenvoyAffected
  • <1.36.10
Fixed in
  • 1.36.10

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

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