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HighVulnerabilityCVE-2026-15176updated 26 Oct 2026, 17:26 UTC

nginx web server flaw: memory corruption, crashes and request injection (CVE-2026-15176)

A bug in the nginx web server can let an outside attacker crash the server or possibly run their own code on it. Some configurations also allow sneaking extra requests into backend servers. Update nginx to a fixed version as soon as possibl

Fix availableOfficial, 2 sources
SeverityHighVulnerability
Being exploited?UnclearNo reports either way yet
Fix available?YesUpdated nginx packages published in DSA-6575-1 (Debian) and USN-8955-1 (Ubuntu); specific fixed version numbers not stated in the material. · since 26 Oct 2026
How sure is this?Official, 2 sourcesBacked by an official source

How the attack works simplified

  1. 1Remote attackerSends crafted HTTP or HTTP/3 requests
  2. 2nginx processes requestVulnerable alias, map or buffer handling
  3. 3Memory corruptedBuffer overflow or use-after-free occurs
  4. 4Crash or misuseDenial of service or possible code execution
  5. ResultServer crashes, or attacker gains control

What happened

Debian DSA-6575-1 and Ubuntu USN-8955-1 cover several nginx flaws: a buffer overflow in the alias directive when mapping rewritten URIs to filesystem paths (CVE-2026-15176), buffer overflows in string expression evaluation in HTTP and stream modules (CVE-2026-93479), mishandled fragmented unknown HTTP/3 frames (CVE-2026-95101), an async operation counter overflow causing use-after-free (CVE-2026-97205), and incomplete TLS session ticket key synchronisation between workers (CVE-2026-97629).

Why it is dangerous: Depending on configuration, attackers may crash nginx, corrupt memory, possibly execute code, inject requests into backend servers, bypass request body size limits, or bypass client certificate authentication. Sites using nginx as a web or reverse proxy server are at risk.

Are you affected?

You are affected if you run nginx with the alias directive plus rewrite rules, map directives using regex, HTTP/3 with proxy_request_buffering, SSI pages with asynchronous file I/O, or a shared SSL session cache without explicit ticket key rotation.

nginx packages in Debian (trixie) and Ubuntu releases including 24.04 LTS, 26.04 LTS and 26.10; exact versions not stated in the material.

What to do

  1. Update nginx using your distribution's package manager with the security update from DSA-6575-1 or USN-8955-1
  2. Restart nginx after updating so the fixed code is loaded
  3. If you cannot update right away, review configurations using alias with rewrite, regex map directives, and shared SSL session caches
  4. Explicitly configure SSL session ticket key rotation if you use a shared session cache

Timeline

  1. 21 Oct 2026, 00:00 UTC
    Publicly disclosed
  2. 21 Oct 2026, 00:00 UTC
    Reported by Debian DSA · Debian DSA
  3. 26 Oct 2026, 17:26 UTC
    Ubuntu Security reported on it · Ubuntu Security

Sources 2 reports, oldest first

Official vendor, government CERT or advisory database

Technical details

ID
CVE-2026-15176
EPSS
0.8% chance of exploitation within 30 days
Disclosed
21 Oct 2026, 00:00 UTC
On Zero Radar
before the radar started
Last change
26 Oct 2026, 17:26 UTC

The plain-language parts and the attack diagram were written by an AI model (anthropic/claude-haiku-5.5) from the sources above. Facts like versions, exploitation and dates come from the sources themselves. How Zero Radar works

nginx web server flaw: memory corruption, crashes and request injection (CVE-2026-15176) · Zero Radar