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NGINX released stable version 1.30.6 and mainline version 1.31.7 on October 14, 2026, fixing five vulnerabilities. Upgrade to the release matching your branch as soon as possible. The affected configurations include specific alias, rewrite, map, asynchronous I/O, HTTP/3 proxying and TLS session-resumption setups.
One flaw may let a forged TLS session bypass client-certificate verification; three memory-safety flaws can crash a worker and may permit code execution under particular conditions. As of October 15, 2026, NGINX and F5 reported no attacks, and none of the five vulnerabilities appeared in CISA’s Known Exploited Vulnerabilities catalog.
Which NGINX versions fix the five vulnerabilities?
Install NGINX 1.30.6 for the stable branch or 1.31.7 for the mainline branch. Older branches, including 1.28, remain affected unless your operating-system distributor has separately backported the fixes.
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| Vulnerability | Affected releases | Configuration or protocol required | Documented interim action |
|---|---|---|---|
| CVE-2026-15176 | 0.1.29 through 1.31.6 | alias in a location, a URI-changing rewrite, and a read of $request_filename |
Avoid that alias arrangement and stop using $request_filename there |
| CVE-2026-93479 | 1.31.2 through 1.31.6 and 1.30.0 through 1.30.5 | Regex map captures referenced by root or log_format before the map output variable |
Use named captures only inside the regex-match block |
| CVE-2026-97205 | 0.8.11 through 1.31.6 | Asynchronous file I/O (aio) together with SSI pages containing include virtual |
Turn aio off or stop serving SSI pages |
| CVE-2026-95101 | 1.25.0 through 1.31.6 | HTTP/3 proxying with the default proxy_request_buffering on |
Set proxy_request_buffering off |
| CVE-2026-97629 | 1.23.2 through 1.31.6 | Shared ssl_session_cache without explicit ssl_session_ticket_key files |
Remove the shared cache, load explicit ticket keys, or disable session tickets |
How serious are the October 2026 flaws?
The NGINX advisory classifies all five vulnerabilities as medium severity. F5’s CVSS v4.0 assessments, reported by The Hacker News, rate the three memory bugs at 9.2 (Critical), the TLS issue at 8.3 and the HTTP/3 issue at 6.9. Those scores describe potential impact, not evidence that every installation is remotely exploitable.
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The TLS issue can potentially defeat mutual-TLS access controls. The memory flaws require narrowly defined directives and request-processing paths; the AIO/SSI flaw’s code-execution possibility depends on Address Space Layout Randomization (ASLR) being disabled or bypassed. The HTTP/3 issue requires an HTTP/3-to-upstream proxying path. A separate rewrite-module vulnerability, CVE-2026-42945, was reported as exploited within days of disclosure in May 2026, but it is not one of these October five.
What each vulnerability does
CVE-2026-15176: alias and rewrite heap overflow
A location that combines alias, a rewrite that changes the URI and a read of $request_filename can overflow a heap buffer in an NGINX worker process. The result may be a worker crash and possibly code execution. The exposure is configuration-specific rather than a property of every alias directive.
Until you upgrade, remove the risky alias arrangement in the affected location and avoid reading $request_filename there. Review inherited and included configuration files, not only the main server block.
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A regex-based map can overflow a heap buffer when its captures are referenced by root or log_format before the map’s output variable has been evaluated. The interim guidance is to keep named captures inside the regex-match block and not use them outside that scope in a way that triggers early evaluation.
CVE-2026-97205: asynchronous I/O and SSI use-after-free
When aio handles file operations for SSI pages containing include virtual, a pending operation can outlive the request memory it relies on. That can cause a crash or memory corruption and may allow code execution if ASLR is disabled or bypassed.
Set aio off where this content is served, or disable SSI processing and remove the affected virtual includes until the fixed package is installed. This may trade some file-I/O performance for safety, so test the affected content path after changing it.
CVE-2026-95101: HTTP/3 request-body injection
With HTTP/3 enabled and NGINX proxying requests upstream while proxy_request_buffering remains at its default value of on, an unknown frame split across reads can be interpreted as request-body data. NGINX may then forward that data upstream outside the configured client_max_body_size limit.
The cited workaround is proxy_request_buffering off on the affected proxy location. This changes when request data is sent upstream, so verify upstream timeout, upload and streaming behavior.
CVE-2026-97629: TLS session forgery
A shared ssl_session_cache without explicitly configured ssl_session_ticket_key files uses automatic ticket-key rotation. F5 says uninitialized key material can, in a non-deterministic way outside an attacker’s control, permit a forged TLS session. A successful forgery could bypass client-certificate verification and expose resources protected by mutual TLS.
Install the fixed release. If that is delayed, remove the shared session cache, provide explicit ticket-key files, or set ssl_session_tickets off. Servers that already have ssl_session_tickets off are not affected by this vulnerability.
How to check whether a server is exposed
- Run
nginx -Twith the privileges and configuration path used by the service. Save the rendered configuration, including included files, for review. - Search for locations that contain
aliastogether with URI-changing rewrites and$request_filename. - Find regex
mapblocks and check whether captures are consumed byrootorlog_formatbefore the map output variable is evaluated. - Identify servers that enable
aioand serve SSI pages usinginclude virtual. - Inventory HTTP/3 or QUIC listeners and the proxy locations behind them. Confirm whether those locations leave
proxy_request_bufferingenabled. - Check TLS server blocks for a shared
ssl_session_cache, explicitssl_session_ticket_keyfiles and the value ofssl_session_tickets. - Record whether mutual TLS protects an administrative or sensitive endpoint, and whether ASLR is enabled on the host. These facts determine the practical impact of the TLS and memory issues.
Upgrade and mitigation plan
1. Patch the NGINX package
Upgrade to 1.30.6 or 1.31.7, then validate the binary and configuration before restarting. If your operating system supplies NGINX, check its package changelog to confirm that the October fixes were backported when the version number is older than those upstream releases.
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2. Apply temporary controls if maintenance is delayed
- Remove the vulnerable
alias/rewrite/$request_filenamecombination. - Constrain regex-map captures to the matching block and remove early references from
rootandlog_format. - Disable
aioor SSI for pages using virtual includes. - Set
proxy_request_buffering offon HTTP/3 proxy locations. - Remove the shared TLS session cache, load explicit ticket keys, or disable session tickets.
3. Re-test security-sensitive behavior
After upgrading or changing directives, test normal TLS handshakes and failed client-certificate handshakes, especially for mutual-TLS protected resources. Also test HTTP/3 uploads, SSI pages, rewritten aliased paths and log formats that use map captures. Review worker logs for crashes or configuration errors before returning traffic to all instances.
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What administrators should prioritize
Start with externally reachable HTTP/3 proxy endpoints and any mutual-TLS service because those flaws affect request handling and authentication directly. Next review the three memory-bug configurations, paying particular attention to shared snippets and generated configuration that may hide the triggering directives. Keep ASLR enabled, but do not treat it as a substitute for patching: the advisory describes it as a condition affecting exploitability of one memory flaw, not as a complete defense.
The release announcement stated that one of the five vulnerabilities exists in every NGINX release since May 2005. That historical reach makes version inventory important, but exploitation still depends on the specific directive combinations listed above.
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